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Puljak, E.; Pierini, M.; García-Saez, A.
Tensor network for anomaly detection in the latent space of proton collision events at the LHC Artículo de revista
En: Machine Learning: Science and Technology, vol. 6, iss. 4, no 045001, 2026.
Resumen | Enlaces | BibTeX | Etiquetas: BSC
@article{nokey,
title = {Tensor network for anomaly detection in the latent space of proton collision events at the LHC},
author = {Puljak, E. and Pierini, M. and García-Saez, A.},
url = {https://iopscience.iop.org/article/10.1088/2632-2153/ae0243/meta},
doi = {10.1088/2632-2153/ae0243},
year = {2026},
date = {2026-10-06},
journal = {Machine Learning: Science and Technology},
volume = {6},
number = {045001},
issue = {4},
abstract = {The pursuit of discovering new phenomena at the Large Hadron Collider (LHC) requires constant innovation in algorithms and technologies. Tensor networks are mathematical models at the intersection of classical and quantum machine learning, which present a promising and efficient alternative for tackling these challenges. In this study, we propose a tensor network-based strategy for anomaly detection at the LHC and demonstrate its superior performance in identifying new phenomena compared to established quantum methods. Our model is a parameterized matrix product state with an isometric feature map, processing a latent representation of simulated LHC data generated by an autoencoder. Our results highlight the potential of tensor networks to enhance new-physics discovery.},
keywords = {BSC},
pubstate = {published},
tppubtype = {article}
}
The pursuit of discovering new phenomena at the Large Hadron Collider (LHC) requires constant innovation in algorithms and technologies. Tensor networks are mathematical models at the intersection of classical and quantum machine learning, which present a promising and efficient alternative for tackling these challenges. In this study, we propose a tensor network-based strategy for anomaly detection at the LHC and demonstrate its superior performance in identifying new phenomena compared to established quantum methods. Our model is a parameterized matrix product state with an isometric feature map, processing a latent representation of simulated LHC data generated by an autoencoder. Our results highlight the potential of tensor networks to enhance new-physics discovery.
P. Koushik Chandarana, P.; Kasturi Ranjan, S.; Chen, X.; Del Campo, A.
Lyapunov Controlled Counterdiabatic Quantum Optimization Artículo de revista
En: 2026.
Resumen | Enlaces | BibTeX | Etiquetas: UPV/EHU
@article{nokey,
title = {Lyapunov Controlled Counterdiabatic Quantum Optimization},
author = {Chandarana, P. Koushik, P. and Kasturi Ranjan, S. and Chen, X. and Del Campo, A. },
url = {https://iopscience.iop.org/article/10.1088/2058-9565/ae7d4e},
doi = {10.1088/2058-9565/ae7d4e},
year = {2026},
date = {2026-06-25},
urldate = {2024-09-19},
abstract = {We introduce a quantum algorithm that integrates counterdiabatic (CD) protocols with quantum Lyapunov control (QLC) to address combinatorial optimization problems. This approach offers versatility, allowing implementation as either a digital-analog or purely digital algorithm based on selected control strategies. By examining spin-glass Hamiltonians, we illustrate how the algorithm can explore alternative paths to enhance solution outcomes compared to conventional CD techniques. This method reduces dependence on extensive higher-order CD terms and on classical optimization techniques, making it more suitable for existing quantum computing platforms. The combination of digital compression via CD protocols and the adaptable nature of QLC methods positions this approach as a promising candidate for near-term quantum devices.},
howpublished = {Preprint},
keywords = {UPV/EHU},
pubstate = {published},
tppubtype = {article}
}
We introduce a quantum algorithm that integrates counterdiabatic (CD) protocols with quantum Lyapunov control (QLC) to address combinatorial optimization problems. This approach offers versatility, allowing implementation as either a digital-analog or purely digital algorithm based on selected control strategies. By examining spin-glass Hamiltonians, we illustrate how the algorithm can explore alternative paths to enhance solution outcomes compared to conventional CD techniques. This method reduces dependence on extensive higher-order CD terms and on classical optimization techniques, making it more suitable for existing quantum computing platforms. The combination of digital compression via CD protocols and the adaptable nature of QLC methods positions this approach as a promising candidate for near-term quantum devices.
deMarti iOlius, A.; Etxezarreta Martinez, I.; Roffe, J.; Etxezarreta Martinez, J.
An almost-linear time decoding algorithm for quantum LDPC codes under circuit-level noise Artículo de revista
En: npj Quantum Information, 2026.
Resumen | Enlaces | BibTeX | Etiquetas: TECNUN
@article{nokey,
title = {An almost-linear time decoding algorithm for quantum LDPC codes under circuit-level noise},
author = {deMarti iOlius, A. and Etxezarreta Martinez, I. and Roffe, J. and Etxezarreta Martinez, J. },
url = {https://www.nature.com/articles/s41534-026-01292-1},
doi = {doi.org/10.1038/s41534-026-01292-1},
year = {2026},
date = {2026-06-09},
urldate = {2024-09-02},
journal = {npj Quantum Information},
abstract = {Fault-tolerant quantum computers must be designed in conjunction with classical co-processors that decode quantum error correction measurement information in real-time. In this work, we introduce the belief propagation plus ordered Tanner forest (BP + OTF) algorithm as an almost-linear time decoder for quantum low-density parity-check codes. The OTF post-processing stage removes qubits from the decoding graph until it has a tree-like structure. Provided that the resultant loop-free OTF graph supports a subset of qubits that can generate the syndrome, BP decoding is then guaranteed to converge. To enhance performance under circuit-level noise, we introduce a technique for sparsifying detector error models. This method uses a transfer matrix to map soft information from the full detector graph to the sparsified graph, preserving critical error propagation information from the syndrome extraction circuit. Our BP+OTF implementation first applies standard BP to the full detector graph, followed by BP + OTF post-processing on the sparsified graph. Numerical simulations show that the BP+OTF decoder achieves similar logical error suppression compared to state-of-the-art inversion-based and matching decoders for bivariate bicycle and surface codes, respectively, while maintaining almost-linear runtime complexity across all stages.},
keywords = {TECNUN},
pubstate = {published},
tppubtype = {article}
}
Fault-tolerant quantum computers must be designed in conjunction with classical co-processors that decode quantum error correction measurement information in real-time. In this work, we introduce the belief propagation plus ordered Tanner forest (BP + OTF) algorithm as an almost-linear time decoder for quantum low-density parity-check codes. The OTF post-processing stage removes qubits from the decoding graph until it has a tree-like structure. Provided that the resultant loop-free OTF graph supports a subset of qubits that can generate the syndrome, BP decoding is then guaranteed to converge. To enhance performance under circuit-level noise, we introduce a technique for sparsifying detector error models. This method uses a transfer matrix to map soft information from the full detector graph to the sparsified graph, preserving critical error propagation information from the syndrome extraction circuit. Our BP+OTF implementation first applies standard BP to the full detector graph, followed by BP + OTF post-processing on the sparsified graph. Numerical simulations show that the BP+OTF decoder achieves similar logical error suppression compared to state-of-the-art inversion-based and matching decoders for bivariate bicycle and surface codes, respectively, while maintaining almost-linear runtime complexity across all stages.
Fanizza, M.; Rouzé, C.; Stilck França, D.
Efficient Hamiltonian, structure and trace distance learning of Gaussian states Working paper
2026.
Resumen | Enlaces | BibTeX | Etiquetas: UAB
@workingpaper{nokey,
title = {Efficient Hamiltonian, structure and trace distance learning of Gaussian states},
author = {Fanizza, M. and Rouzé, C. and Stilck França, D.},
url = {https://arxiv.org/abs/2411.03163},
doi = {doi.org/10.48550/arXiv.2411.03163},
year = {2026},
date = {2026-06-01},
urldate = {2025-04-07},
abstract = {In this work, we initiate the study of Hamiltonian learning for positive temperature bosonic Gaussian states, the quantum generalization of the widely studied problem of learning Gaussian graphical models. We obtain efficient protocols, both in sample and computational complexity, for the task of inferring the parameters of their underlying quadratic Hamiltonian under the assumption of bounded temperature, squeezing, displacement and maximal degree of the interaction graph. Our protocol only requires heterodyne measurements, which are often experimentally feasible, and has a sample complexity that scales logarithmically with the number of modes. Furthermore, we show that it is possible to learn the underlying interaction graph in a similar setting and sample complexity. Taken together, our results put the status of the quantum Hamiltonian learning problem for continuous variable systems in a more advanced state when compared to spins, where state-of-the-art results are either unavailable or quantitatively inferior to ours. In addition, we use our techniques to obtain the first results on learning Gaussian states in trace distance with a quadratic scaling in precision and polynomial in the number of modes, albeit imposing certain restrictions on the Gaussian states. Our main technical innovations are several continuity bounds for the covariance and Hamiltonian matrix of a Gaussian state, which are of independent interest, combined with what we call the local inversion technique. In essence, the local inversion technique allows us to reliably infer the Hamiltonian of a Gaussian state by only estimating in parallel submatrices of the covariance matrix whose size scales with the desired precision, but not the number of modes. This way we bypass the need to obtain precise global estimates of the covariance matrix, controlling the sample complexity.},
keywords = {UAB},
pubstate = {published},
tppubtype = {workingpaper}
}
In this work, we initiate the study of Hamiltonian learning for positive temperature bosonic Gaussian states, the quantum generalization of the widely studied problem of learning Gaussian graphical models. We obtain efficient protocols, both in sample and computational complexity, for the task of inferring the parameters of their underlying quadratic Hamiltonian under the assumption of bounded temperature, squeezing, displacement and maximal degree of the interaction graph. Our protocol only requires heterodyne measurements, which are often experimentally feasible, and has a sample complexity that scales logarithmically with the number of modes. Furthermore, we show that it is possible to learn the underlying interaction graph in a similar setting and sample complexity. Taken together, our results put the status of the quantum Hamiltonian learning problem for continuous variable systems in a more advanced state when compared to spins, where state-of-the-art results are either unavailable or quantitatively inferior to ours. In addition, we use our techniques to obtain the first results on learning Gaussian states in trace distance with a quadratic scaling in precision and polynomial in the number of modes, albeit imposing certain restrictions on the Gaussian states. Our main technical innovations are several continuity bounds for the covariance and Hamiltonian matrix of a Gaussian state, which are of independent interest, combined with what we call the local inversion technique. In essence, the local inversion technique allows us to reliably infer the Hamiltonian of a Gaussian state by only estimating in parallel submatrices of the covariance matrix whose size scales with the desired precision, but not the number of modes. This way we bypass the need to obtain precise global estimates of the covariance matrix, controlling the sample complexity.
Bou-Comas, A.; Marimón, C. R.; Schneider, J. T.; Ramos Marimón, C.; Schneider, J. T.; Carignano, S.; Tagliacozzo, L.
Measuring temporal entanglement in experiments Artículo de revista
En: 2026.
Resumen | Enlaces | BibTeX | Etiquetas: CSIC-4.7
@article{nokey,
title = {Measuring temporal entanglement in experiments},
author = {Bou-Comas, A. and Marimón, C.R. and Schneider, J.T. and Ramos Marimón, C. and Schneider, J.T. and Carignano, S. and Tagliacozzo, L. },
url = {https://journals.aps.org/prresearch/abstract/10.1103/436b-cnh8},
doi = {doi.org/10.1103/436b-cnh8},
year = {2026},
date = {2026-06-01},
urldate = {2025-09-09},
abstract = {We propose an experimental protocol to measure generalized temporal entropies in many-body quantum systems. Our approach involves using local operators as probes to characterize the out-of-equilibrium dynamics induced by a geometric double quench on a replicated system. Such protocol mimics the path integral on the corresponding Riemann surface encoding generalized temporal entanglement. We present the results of tensor network simulations of one-dimensional systems that validate the protocol and demonstrate the experimental feasibility of measuring generalized temporal entropies, and we outline the experimental requirements for implementing these quenches using state-of-the-art quantum simulators. Therefore, our results provide a physical interpretation of the meaning of generalized temporal entropies. Furthermore, they reveal that the dynamics induced on two replicas of the Ising model in a transverse field differ qualitatively from those of its nonintegrable extension, suggesting that generalized temporal entropies can be used as a tool for identifying different dynamical classes in quantum systems.},
keywords = {CSIC-4.7},
pubstate = {published},
tppubtype = {article}
}
We propose an experimental protocol to measure generalized temporal entropies in many-body quantum systems. Our approach involves using local operators as probes to characterize the out-of-equilibrium dynamics induced by a geometric double quench on a replicated system. Such protocol mimics the path integral on the corresponding Riemann surface encoding generalized temporal entanglement. We present the results of tensor network simulations of one-dimensional systems that validate the protocol and demonstrate the experimental feasibility of measuring generalized temporal entropies, and we outline the experimental requirements for implementing these quenches using state-of-the-art quantum simulators. Therefore, our results provide a physical interpretation of the meaning of generalized temporal entropies. Furthermore, they reveal that the dynamics induced on two replicas of the Ising model in a transverse field differ qualitatively from those of its nonintegrable extension, suggesting that generalized temporal entropies can be used as a tool for identifying different dynamical classes in quantum systems.
Capel, A.; Alhambra, A. M.; Gondolf, P.; Ruiz-de-Alarcón, A.; Scalet, S. O.
Conditional Independence of 1D Gibbs States with Applications to Efficient Learning Artículo de revista
En: Annales Henri Poincaré, 2026.
Resumen | Enlaces | BibTeX | Etiquetas: UCM-4.3
@article{nokey,
title = {Conditional Independence of 1D Gibbs States with Applications to Efficient Learning},
author = {Capel, A. and Alhambra, A.M. and Gondolf, P. and Ruiz-de-Alarcón, A. and Scalet, S.O.},
url = {https://link.springer.com/article/10.1007/s00023-026-01655-6},
doi = {doi.org/10.1007/s00023-026-01655-6},
year = {2026},
date = {2026-05-05},
urldate = {2026-05-05},
journal = {Annales Henri Poincaré},
abstract = {We show that spin chains in thermal equilibrium have a correlation structure in which individual regions are strongly correlated at most with their near vicinity. We quantify this with alternative notions of the conditional mutual information, defined through the so-called Belavkin–Staszewski relative entropy. We prove that these measures decay superexponentially at every positive temperature, under the assumption that the spin chain Hamiltonian is translation-invariant. Using a recovery map associated with these measures, we sequentially construct tensor network approximations in terms of marginals of small (sublogarithmic) size. As a main application, we show that classical representations of the states can be learned efficiently from local measurements with a polynomial sample complexity. We also prove an approximate factorization condition for the purity of the entire Gibbs state, which implies that it can be efficiently estimated to a small multiplicative error from a small number of local measurements. The results extend from strictly local to exponentially-decaying interactions above a threshold temperature, albeit only with exponential decay rates. As a technical step of independent interest, we show an upper bound to the decay of the Belavkin–Staszewski relative entropy upon the application of a conditional expectation.},
keywords = {UCM-4.3},
pubstate = {published},
tppubtype = {article}
}
We show that spin chains in thermal equilibrium have a correlation structure in which individual regions are strongly correlated at most with their near vicinity. We quantify this with alternative notions of the conditional mutual information, defined through the so-called Belavkin–Staszewski relative entropy. We prove that these measures decay superexponentially at every positive temperature, under the assumption that the spin chain Hamiltonian is translation-invariant. Using a recovery map associated with these measures, we sequentially construct tensor network approximations in terms of marginals of small (sublogarithmic) size. As a main application, we show that classical representations of the states can be learned efficiently from local measurements with a polynomial sample complexity. We also prove an approximate factorization condition for the purity of the entire Gibbs state, which implies that it can be efficiently estimated to a small multiplicative error from a small number of local measurements. The results extend from strictly local to exponentially-decaying interactions above a threshold temperature, albeit only with exponential decay rates. As a technical step of independent interest, we show an upper bound to the decay of the Belavkin–Staszewski relative entropy upon the application of a conditional expectation.
Florido-Llinàs, M.; Alhambra, A. M.; Pérez-García, D.; Cirac, J. I.
Regular language quantum states Artículo de revista
En: Quantum, 2026.
Resumen | Enlaces | BibTeX | Etiquetas: UCM-4.2
@article{nokey,
title = {Regular language quantum states},
author = {Florido-Llinàs, M. and Alhambra, A.M. and Pérez-García, D. and Cirac, J.I. },
url = {https://quantum-journal.org/papers/q-2026-04-29-2089/#},
doi = {doi.org/10.22331/q-2026-04-29-2089},
year = {2026},
date = {2026-04-29},
urldate = {2024-07-24},
journal = {Quantum},
abstract = {We introduce regular language states, a family of quantum many-body states. They are built from a special class of formal languages, called regular, which has been thoroughly studied in the field of computer science. They can be understood as the superposition of all the words in a regular language and encompass physically relevant states such as the GHZ-, W- or Dicke-states. By leveraging the theory of regular languages, we develop a theoretical framework to describe them. First, we express them in terms of matrix product states, providing efficient criteria to recognize them. We then develop a canonical form which allows us to formulate a fundamental theorem for the equivalence of regular language states, including under local unitary operations. We also exploit the theory of tensor networks to find an efficient criterion to determine when regular languages are shift-invariant.
},
keywords = {UCM-4.2},
pubstate = {published},
tppubtype = {article}
}
We introduce regular language states, a family of quantum many-body states. They are built from a special class of formal languages, called regular, which has been thoroughly studied in the field of computer science. They can be understood as the superposition of all the words in a regular language and encompass physically relevant states such as the GHZ-, W- or Dicke-states. By leveraging the theory of regular languages, we develop a theoretical framework to describe them. First, we express them in terms of matrix product states, providing efficient criteria to recognize them. We then develop a canonical form which allows us to formulate a fundamental theorem for the equivalence of regular language states, including under local unitary operations. We also exploit the theory of tensor networks to find an efficient criterion to determine when regular languages are shift-invariant.
Baghali Khanian, Z.; Winter, A.
A Rate-Distortion Perspective on Quantum State Redistribution Artículo de revista
En: IEEE Transactions on Information Theory, 2026.
Resumen | Enlaces | BibTeX | Etiquetas: UAB
@article{nokey,
title = {A Rate-Distortion Perspective on Quantum State Redistribution},
author = {Baghali Khanian, Z. and Winter, A. },
url = {https://ieeexplore.ieee.org/document/10795756},
doi = {10.1109/TIT.2024.3516505},
year = {2026},
date = {2026-04-01},
urldate = {2025-12-12},
journal = {IEEE Transactions on Information Theory},
abstract = {We consider a rate-distortion version of the quantum state redistribution task, where the error of the decoded state is judged via an additive distortion measure; it thus constitutes a quantum generalisation of the classical Wyner-Ziv problem. The quantum source is described by a tripartite pure state shared between Alice (A, encoder), Bob (B, decoder) and a reference (R). Both Alice and Bob are required to output a system (Ã and B̃, respectively), and the distortion measure is encoded in an observable on ÃB̃R. It includes as special cases most quantum rate-distortion problems considered in the past, and in particular quantum data compression with the fidelity measured per copy; furthermore, it generalises the well-known state merging and quantum state redistribution tasks for a pure state source, with per-copy fidelity, and a variant recently considered by us, where the source is an ensemble of pure states [ZBK & AW, Proc. ISIT 2020, pp. 1858-1863 and ZBK, PhD thesis, UAB 2020, arXiv:2012.14143]. We derive a single-letter formula for the rate-distortion function of compression schemes assisted by free entanglement. A peculiarity of the formula is that in general it requires optimisation over an unbounded auxiliary register, so the rate-distortion function is not readily computable from our result, and there is a continuity issue at zero distortion. However, we show how to overcome these difficulties in certain situations.},
keywords = {UAB},
pubstate = {published},
tppubtype = {article}
}
We consider a rate-distortion version of the quantum state redistribution task, where the error of the decoded state is judged via an additive distortion measure; it thus constitutes a quantum generalisation of the classical Wyner-Ziv problem. The quantum source is described by a tripartite pure state shared between Alice (A, encoder), Bob (B, decoder) and a reference (R). Both Alice and Bob are required to output a system (Ã and B̃, respectively), and the distortion measure is encoded in an observable on ÃB̃R. It includes as special cases most quantum rate-distortion problems considered in the past, and in particular quantum data compression with the fidelity measured per copy; furthermore, it generalises the well-known state merging and quantum state redistribution tasks for a pure state source, with per-copy fidelity, and a variant recently considered by us, where the source is an ensemble of pure states [ZBK & AW, Proc. ISIT 2020, pp. 1858-1863 and ZBK, PhD thesis, UAB 2020, arXiv:2012.14143]. We derive a single-letter formula for the rate-distortion function of compression schemes assisted by free entanglement. A peculiarity of the formula is that in general it requires optimisation over an unbounded auxiliary register, so the rate-distortion function is not readily computable from our result, and there is a continuity issue at zero distortion. However, we show how to overcome these difficulties in certain situations.
García-Azorín, P.; Cárdenas-López, F. A.; Huber, H. B. P.; Romero, G.; Werninghaus, M.; Motzoi, F.; Filipp, S.; Sanz, M. (Ed.)
Robust multi-mode superconducting circuit optimized for quantum information processing Working paper
2026.
Resumen | Enlaces | BibTeX | Etiquetas: UPV/EHU
@workingpaper{nokey,
title = {Robust multi-mode superconducting circuit optimized for quantum information processing},
editor = {García-Azorín, P. and Cárdenas-López, F.A. and Huber, H.B.P. and Romero, G. and Werninghaus, M. and Motzoi, F. and Filipp, S. and Sanz, M.},
url = {https://arxiv.org/abs/2407.18895},
doi = {doi.org/10.48550/arXiv.2407.18895},
year = {2026},
date = {2026-03-21},
urldate = {2026-03-21},
abstract = {Multi-mode superconducting circuits offer a promising platform for engineering robust systems for quantum computation. Previous studies indicate that single-mode devices cannot be engineered to simultaneously exhibit resilience against multiple decoherence sources due to conflicting requirements. In contrast, multi-mode systems offer increased flexibility and have proven capable of overcoming these fundamental limitations. Here, we present a multi-mode device optimized for quantum information processing. It features an anharmonicity of a third of the qubit frequency and reduced energy dispersion caused by charge and magnetic flux fluctuations. It exhibits improvements over the fundamental errors limiting Transmon and Fluxonium coherence and control, achieving ratios between the total coherence time and the gate time T2/tg one order of magnitude larger than Transmon and two times larger than Fluxonium for microwave charge drives, assuming equal dielectric and inductive loss quality factors and limited drive strength. It furthermore demonstrates robustness against fabrication errors, a major limitation in many proposed multi-mode devices.},
keywords = {UPV/EHU},
pubstate = {published},
tppubtype = {workingpaper}
}
Multi-mode superconducting circuits offer a promising platform for engineering robust systems for quantum computation. Previous studies indicate that single-mode devices cannot be engineered to simultaneously exhibit resilience against multiple decoherence sources due to conflicting requirements. In contrast, multi-mode systems offer increased flexibility and have proven capable of overcoming these fundamental limitations. Here, we present a multi-mode device optimized for quantum information processing. It features an anharmonicity of a third of the qubit frequency and reduced energy dispersion caused by charge and magnetic flux fluctuations. It exhibits improvements over the fundamental errors limiting Transmon and Fluxonium coherence and control, achieving ratios between the total coherence time and the gate time T2/tg one order of magnitude larger than Transmon and two times larger than Fluxonium for microwave charge drives, assuming equal dielectric and inductive loss quality factors and limited drive strength. It furthermore demonstrates robustness against fabrication errors, a major limitation in many proposed multi-mode devices.
Gopalkrishna Naik, S.; Zartab, M.; Gisin, N.; Banik, M.
No-Go Theorem for Generic Simulation of Qubit Channels with Finite Classical Resources Artículo de revista
En: The Royal Society, 2026.
Resumen | Enlaces | BibTeX | Etiquetas: UAB
@article{nokey,
title = {No-Go Theorem for Generic Simulation of Qubit Channels with Finite Classical Resources},
author = {Gopalkrishna Naik, S. and Zartab, M. and Gisin, N. and Banik, M. },
url = {https://royalsocietypublishing.org/rspa/article/482/2333/20250831/480860/No-go-theorem-for-generic-simulation-of-qubit},
doi = {doi.org/10.1098/rspa.2025.0831},
year = {2026},
date = {2026-03-11},
urldate = {2025-07-16},
journal = {The Royal Society},
abstract = {Can quantum processes be simulated using only classical resources? This question delineates the boundary between classical and quantum models and clarifies the origin of quantum advantage in information processing. We address this question through the task of quantum channel simulation, where a sender (Alice) holds the classical description of a quantum state and wishes to transmit it to a receiver (Bob) for measurement. Prior work has shown that, for qubit channels, 2 bits of forward communication with shared randomness suffice to reproduce the statistics of any single-qubit measurement. We argue, however, that true channel simulation requires reproducing statistics of joint measurements—including entangled effects—on Alice’s state and an auxiliary system held by Bob. Such scenarios naturally arise in network communication, where some nodes know the state, while others do not. We prove that a perfect qubit channel cannot be simulated with any finite amount of classical communication, even using the most general multi-round, bidirectional protocols. We further show that this no-go result is rooted in the necessity of reproducing statistics associated with entangled effects. On the other hand, we show that noisy qubit channels, such as depolarizing channels, admit classical simulation, though the required communication diverges as noise decreases.},
keywords = {UAB},
pubstate = {published},
tppubtype = {article}
}
Can quantum processes be simulated using only classical resources? This question delineates the boundary between classical and quantum models and clarifies the origin of quantum advantage in information processing. We address this question through the task of quantum channel simulation, where a sender (Alice) holds the classical description of a quantum state and wishes to transmit it to a receiver (Bob) for measurement. Prior work has shown that, for qubit channels, 2 bits of forward communication with shared randomness suffice to reproduce the statistics of any single-qubit measurement. We argue, however, that true channel simulation requires reproducing statistics of joint measurements—including entangled effects—on Alice’s state and an auxiliary system held by Bob. Such scenarios naturally arise in network communication, where some nodes know the state, while others do not. We prove that a perfect qubit channel cannot be simulated with any finite amount of classical communication, even using the most general multi-round, bidirectional protocols. We further show that this no-go result is rooted in the necessity of reproducing statistics associated with entangled effects. On the other hand, we show that noisy qubit channels, such as depolarizing channels, admit classical simulation, though the required communication diverges as noise decreases.
Casas, B.; Mieldzioć, G. R.; Ahmad, S.; Płodzień, M.; Bruzda, W.; Cervera-Lierta, A.; Życzkowski, K.
Quantum Circuits for High-Dimensional Absolutely Maximally Entangled States Artículo de revista
En: Quantum Science and Technology, 2026.
Resumen | Enlaces | BibTeX | Etiquetas: BSC
@article{nokey,
title = {Quantum Circuits for High-Dimensional Absolutely Maximally Entangled States},
author = {Casas, B. and Mieldzioć, G.R. and Ahmad, S. and Płodzień, M. and Bruzda, W. and Cervera-Lierta, A. and Życzkowski, K. },
url = {https://iopscience.iop.org/article/10.1088/2058-9565/ae46d6},
doi = {10.1088/2058-9565/ae46d6},
year = {2026},
date = {2026-02-26},
urldate = {2025-04-07},
journal = {Quantum Science and Technology},
abstract = {Absolutely maximally entangled (AME) states of multipartite quantum systems exhibit maximal entanglement across all possible bipartitions. These states lead to teleportation protocols that surpass standard teleportation schemes, determine quantum error correction codes and can be used to test performance of current term quantum processors. Several AME states can be constructed from graph states using minimal quantum resources. However, there exist other constructions that depart from the stabilizer formalism. In this work, we present explicit quantum circuits to generate exemplary non-stabilizer AME states of four subsystems with four, six, and eight levels each and analyze their capabilities to perform quantum information tasks.
},
keywords = {BSC},
pubstate = {published},
tppubtype = {article}
}
Absolutely maximally entangled (AME) states of multipartite quantum systems exhibit maximal entanglement across all possible bipartitions. These states lead to teleportation protocols that surpass standard teleportation schemes, determine quantum error correction codes and can be used to test performance of current term quantum processors. Several AME states can be constructed from graph states using minimal quantum resources. However, there exist other constructions that depart from the stabilizer formalism. In this work, we present explicit quantum circuits to generate exemplary non-stabilizer AME states of four subsystems with four, six, and eight levels each and analyze their capabilities to perform quantum information tasks.
Etxezarreta Martinez, J.; Schnabl, P.; Oliva del Moral, P.; Dastbasteh, R.; Crespo, P. M.; Otxoa, R. M.
Leveraging biased noise for more efficient quantum error correction at the circuit-level with two-level qubits Artículo de revista
En: Physical Review Applied, 2026.
Resumen | Enlaces | BibTeX | Etiquetas: TECNUN
@article{nokey,
title = {Leveraging biased noise for more efficient quantum error correction at the circuit-level with two-level qubits},
author = {Etxezarreta Martinez, J. and Schnabl, P. and Oliva del Moral, P. and Dastbasteh, R. and Crespo, P.M. and Otxoa, R.M.},
url = {https://journals.aps.org/prapplied/abstract/10.1103/q7w6-nljp},
doi = {doi.org/10.1103/q7w6-nljp},
year = {2026},
date = {2026-01-09},
urldate = {2025-05-23},
journal = {Physical Review Applied},
abstract = {Tailoring quantum-error-correction codes (QECCs) to biased noise has demonstrated significant benefits. However, most of the prior research on this topic has focused on code-capacity noise models. Furthermore, a no-go theorem prevents the construction of controlled-not (cnot) gates for two-level qubits in a bias-preserving manner which may, in principle, imply that noise bias cannot be leveraged in such systems. In this work, we show that a residual bias up to 𝜂 ∼5 can be maintained in cnot gates under certain conditions. Moreover, we employ controlled-Z (cz) gates in syndrome-extraction circuits and show how to natively implement these in a bias-preserving manner for a broad class of qubit platforms. This motivates the introduction of what we call a hybrid biased-depolarizing (HBD) circuit-level noise model that captures these features. We numerically study the performance of the 𝑋𝑍𝑍𝑋 surface code and observe that bias-preserving cz gates are critical for leveraging biased noise. Accounting for the residual bias present in the cnot gates, we observe an increase in the code threshold up to a 1.27% physical error rate, representing a 90% improvement. Additionally, we find that the required qubit footprint can be reduced by up to 75% at relevant physical error rates.},
keywords = {TECNUN},
pubstate = {published},
tppubtype = {article}
}
Tailoring quantum-error-correction codes (QECCs) to biased noise has demonstrated significant benefits. However, most of the prior research on this topic has focused on code-capacity noise models. Furthermore, a no-go theorem prevents the construction of controlled-not (cnot) gates for two-level qubits in a bias-preserving manner which may, in principle, imply that noise bias cannot be leveraged in such systems. In this work, we show that a residual bias up to 𝜂 ∼5 can be maintained in cnot gates under certain conditions. Moreover, we employ controlled-Z (cz) gates in syndrome-extraction circuits and show how to natively implement these in a bias-preserving manner for a broad class of qubit platforms. This motivates the introduction of what we call a hybrid biased-depolarizing (HBD) circuit-level noise model that captures these features. We numerically study the performance of the 𝑋𝑍𝑍𝑋 surface code and observe that bias-preserving cz gates are critical for leveraging biased noise. Accounting for the residual bias present in the cnot gates, we observe an increase in the code threshold up to a 1.27% physical error rate, representing a 90% improvement. Additionally, we find that the required qubit footprint can be reduced by up to 75% at relevant physical error rates.
Giordano, S.; Martin-Delgado, M. A.
Quantum Algorithm for Testing Graph Completeness Artículo de revista
En: Annals of Physics, 2026.
Resumen | Enlaces | BibTeX | Etiquetas: UCM-4.3
@article{nokey,
title = {Quantum Algorithm for Testing Graph Completeness},
author = {Giordano, S. and Martin-Delgado, M.A.
},
url = {https://www.sciencedirect.com/science/article/pii/S0003491625003872?via%3Dihub},
doi = {doi.org/10.1016/j.aop.2025.170305},
year = {2026},
date = {2026-01-01},
urldate = {2024-08-16},
journal = {Annals of Physics},
abstract = {Testing graph completeness is a critical problem in computer science and network theory. Leveraging quantum computation, we present an efficient algorithm using the Szegedy quantum walk and quantum phase estimation (QPE). Our algorithm, which takes the number of nodes and the adjacency matrix as input, constructs a quantum walk operator and applies QPE to estimate its eigenvalues. These eigenvalues reveal the graph's structural properties, enabling us to determine its completeness. We establish a relationship between the number of nodes in a complete graph and the number of marked nodes, optimizing the success probability and running time. The time complexity of our algorithm is O(log² n), where n is the number of nodes of the graph, offering a clear quantum advantage over classical methods. This approach is useful in network structure analysis, evaluating classical routing algorithms, and assessing systems based on pairwise comparisons.},
keywords = {UCM-4.3},
pubstate = {published},
tppubtype = {article}
}
Testing graph completeness is a critical problem in computer science and network theory. Leveraging quantum computation, we present an efficient algorithm using the Szegedy quantum walk and quantum phase estimation (QPE). Our algorithm, which takes the number of nodes and the adjacency matrix as input, constructs a quantum walk operator and applies QPE to estimate its eigenvalues. These eigenvalues reveal the graph's structural properties, enabling us to determine its completeness. We establish a relationship between the number of nodes in a complete graph and the number of marked nodes, optimizing the success probability and running time. The time complexity of our algorithm is O(log² n), where n is the number of nodes of the graph, offering a clear quantum advantage over classical methods. This approach is useful in network structure analysis, evaluating classical routing algorithms, and assessing systems based on pairwise comparisons.
Lazar, J.; Giner Olavarrieta, S.; Gatti, G.; Argüelles, C.; Sanz, M.
Pathways in neutrino physics via quantum-encoded data analysis Artículo de revista
En: 2025.
Resumen | Enlaces | BibTeX | Etiquetas: UPV/EHU
@article{nokey,
title = {Pathways in neutrino physics via quantum-encoded data analysis},
author = {Lazar, J. and Giner Olavarrieta, S. and Gatti, G. and Argüelles, C. and Sanz, M. },
url = {https://journals.aps.org/prresearch/abstract/10.1103/j7gt-zm6f},
doi = {doi.org/10.1103/j7gt-zm6f},
year = {2025},
date = {2025-11-24},
urldate = {2025-11-24},
abstract = {Ever-increasing amount of data is produced by particle detectors in their quest to unveil the laws of Nature. The large data rate requires the use of specialized triggers that promptly reduce the data rate to a manageable level; however, in doing so, unexpected new phenomena may escape detection. Additionally, the large data rate is increasingly difficult to analyze effectively, which has led to a recent revolution on machine learning techniques. Here, we present a methodology based on recent quantum compression techniques that has the capacity to store exponentially more amount of information than classically available methods. To demonstrate this, we encode the full neutrino telescope event information using parity observables in an IBM quantum processor using 8 qubits. Then we show that we can recover the information stored on the quantum computer with a fidelity of 84%. Finally, we illustrate the use of our protocol by performing a classification task that separates electron-neutrino events to muon-neutrinos events in a neutrino telescope. This new capability would eventually allow us to solve the street light effect in particle physics, where we only record signatures of particles with which we are familiar.},
keywords = {UPV/EHU},
pubstate = {published},
tppubtype = {article}
}
Ever-increasing amount of data is produced by particle detectors in their quest to unveil the laws of Nature. The large data rate requires the use of specialized triggers that promptly reduce the data rate to a manageable level; however, in doing so, unexpected new phenomena may escape detection. Additionally, the large data rate is increasingly difficult to analyze effectively, which has led to a recent revolution on machine learning techniques. Here, we present a methodology based on recent quantum compression techniques that has the capacity to store exponentially more amount of information than classically available methods. To demonstrate this, we encode the full neutrino telescope event information using parity observables in an IBM quantum processor using 8 qubits. Then we show that we can recover the information stored on the quantum computer with a fidelity of 84%. Finally, we illustrate the use of our protocol by performing a classification task that separates electron-neutrino events to muon-neutrinos events in a neutrino telescope. This new capability would eventually allow us to solve the street light effect in particle physics, where we only record signatures of particles with which we are familiar.
O de Almeida, J.; Kleinmann, M.; Sentís, G.
Comparison of confidence regions for quantum state tomography Artículo de revista
En: New Journal of Physics , vol. 25, iss. 11, no 113018, 2025.
Resumen | Enlaces | BibTeX | Etiquetas: ICFO-4.17
@article{nokey,
title = {Comparison of confidence regions for quantum state tomography},
author = {O de Almeida, J. and Kleinmann, M. and Sentís, G. },
url = {https://iopscience.iop.org/article/10.1088/1367-2630/ad06d9},
doi = {10.1088/1367-2630/ad06d9},
year = {2025},
date = {2025-11-13},
urldate = {2025-11-13},
journal = {New Journal of Physics },
volume = {25},
number = {113018},
issue = {11},
abstract = {The quantum state associated to an unknown experimental preparation procedure can be determined by performing quantum state tomography. If the statistical uncertainty in the data dominates over other experimental errors, then a tomographic reconstruction procedure must express this uncertainty. A rigorous way to accomplish this is via statistical confidence regions (CRs) in state space. Naturally, the size of this region decreases when increasing the number of samples, but it also depends critically on the construction method of the region. We compare recent methods for constructing CRs as well as a reference method based on a Gaussian approximation. For the comparison, we propose an operational measure with the finding, that there is a significant difference between methods, but which method is preferable can depend on the details of the state preparation scenario.},
keywords = {ICFO-4.17},
pubstate = {published},
tppubtype = {article}
}
The quantum state associated to an unknown experimental preparation procedure can be determined by performing quantum state tomography. If the statistical uncertainty in the data dominates over other experimental errors, then a tomographic reconstruction procedure must express this uncertainty. A rigorous way to accomplish this is via statistical confidence regions (CRs) in state space. Naturally, the size of this region decreases when increasing the number of samples, but it also depends critically on the construction method of the region. We compare recent methods for constructing CRs as well as a reference method based on a Gaussian approximation. For the comparison, we propose an operational measure with the finding, that there is a significant difference between methods, but which method is preferable can depend on the details of the state preparation scenario.
Florido-Llinàs, M.; Alhambra, A. M.; Trivedi, R.; N. Pérez-García Schuch, D.; Cirac, J. I.
The Product Structure of Matrix Product States under Permutations Artículo de revista
En: 2025.
Resumen | Enlaces | BibTeX | Etiquetas: UCM-4.2
@article{nokey,
title = {The Product Structure of Matrix Product States under Permutations},
author = {Florido-Llinàs, M. and Alhambra, A.M. and Trivedi, R. and Schuch, N. Pérez-García, D. and Cirac, J.I. },
url = {https://journals.aps.org/prxquantum/abstract/10.1103/8sbs-t24w},
doi = {doi.org/10.1103/8sbs-t24w},
year = {2025},
date = {2025-11-11},
urldate = {2024-10-25},
abstract = {Tensor network methods have proved to be highly effective in addressing a wide variety of physical scenarios, including those lacking an intrinsic one-dimensional geometry. In such contexts, it is possible for the problem to exhibit a weak form of permutational symmetry, in the sense that entanglement behaves similarly across any arbitrary bipartition. In this paper, we show that translationally-invariant (TI) matrix product states (MPSs) with this property are trivial, meaning that they are either product states or superpositions of a few of them. The results also apply to non-TI generic MPSs, as well as further relevant examples of MPSs including the 𝑊 state and the Dicke states in an approximate sense. Our findings motivate the usage of Ansätze simpler than tensor networks in systems whose structure is invariant under permutations.},
keywords = {UCM-4.2},
pubstate = {published},
tppubtype = {article}
}
Tensor network methods have proved to be highly effective in addressing a wide variety of physical scenarios, including those lacking an intrinsic one-dimensional geometry. In such contexts, it is possible for the problem to exhibit a weak form of permutational symmetry, in the sense that entanglement behaves similarly across any arbitrary bipartition. In this paper, we show that translationally-invariant (TI) matrix product states (MPSs) with this property are trivial, meaning that they are either product states or superpositions of a few of them. The results also apply to non-TI generic MPSs, as well as further relevant examples of MPSs including the 𝑊 state and the Dicke states in an approximate sense. Our findings motivate the usage of Ansätze simpler than tensor networks in systems whose structure is invariant under permutations.
Abellanet-Vidal, J.; Müller-Rigat, G.; Rajchel-Mieldzioć, G.; Sanpera, A.
Sufficient criteria for absolute separability in arbitrary dimensions via linear map inverses Artículo de revista
En: 2025.
Resumen | Enlaces | BibTeX | Etiquetas: UAB
@article{nokey,
title = {Sufficient criteria for absolute separability in arbitrary dimensions via linear map inverses},
author = {Abellanet-Vidal, J. and Müller-Rigat, G. and Rajchel-Mieldzioć, G. and Sanpera, A.},
url = {https://iopscience.iop.org/article/10.1088/1361-6633/ae0cfa},
doi = {10.1088/1361-6633/ae0cfa},
year = {2025},
date = {2025-10-24},
urldate = {2025-10-24},
abstract = {Quantum states that remain separable (i.e. not entangled) under any global unitary transformation are known as absolutely separable and form a convex set. Despite extensive efforts, the complete characterization of this set remains largely unknown. In this work, we employ linear maps and their inverses to derive new sufficient analytical conditions for absolute separability in arbitrary dimensions, providing extremal points of this set and improving its characterization. Additionally, we employ convex geometry optimization to refine the characterization of the set when multiple non-comparable criteria for absolute separability are available. We also address the closely related problem of characterizing the absolute PPT (positive partial transposition) set, which consists of quantum states that remain positive under partial transposition across all unitary transformations. Finally, we extend our results to multipartite states. We are proud to dedicate our work to Professor Ryszard Horodecki, whose pioneering contributions to the field of quantum entanglement continue to inspire us all. With deep gratitude and respect.},
keywords = {UAB},
pubstate = {published},
tppubtype = {article}
}
Quantum states that remain separable (i.e. not entangled) under any global unitary transformation are known as absolutely separable and form a convex set. Despite extensive efforts, the complete characterization of this set remains largely unknown. In this work, we employ linear maps and their inverses to derive new sufficient analytical conditions for absolute separability in arbitrary dimensions, providing extremal points of this set and improving its characterization. Additionally, we employ convex geometry optimization to refine the characterization of the set when multiple non-comparable criteria for absolute separability are available. We also address the closely related problem of characterizing the absolute PPT (positive partial transposition) set, which consists of quantum states that remain positive under partial transposition across all unitary transformations. Finally, we extend our results to multipartite states. We are proud to dedicate our work to Professor Ryszard Horodecki, whose pioneering contributions to the field of quantum entanglement continue to inspire us all. With deep gratitude and respect.
Espinosa, E. M.; Wu, L. A.
Study on quantum thermalization from thermal initial states in a superconducting quantum computer Artículo de revista
En: 2025.
Resumen | Enlaces | BibTeX | Etiquetas: UPV/EHU
@article{nokey,
title = {Study on quantum thermalization from thermal initial states in a superconducting quantum computer},
author = {Espinosa, E.M. and Wu, L.A.},
url = {https://www.nature.com/articles/s41598-025-19553-y},
doi = {doi.org/10.1038/s41598-025-19553-y},
year = {2025},
date = {2025-10-13},
urldate = {2025-10-13},
abstract = {Quantum thermalization in contemporary quantum devices, in particular quantum computers, has recently attracted significant interest. However, there are few experimental results due to the difficulty in preparing thermal states in quantum systems. In this paper, we propose a protocol to indirectly address this challenge using only pure states. While our protocol does not solve the issue of thermal state preparation, it enables the equivalent study of their dynamics. Moreover, we experimentally validate our protocol using IBM quantum devices, presenting results that demonstrate unusual relaxation in equidistant quenches. We also assess the formalism introduced for the Quantum Mpemba Effect (QME), which provides a framework for comparing the dynamics of different thermal states, we do no observe any unusual behaviour in this case, which is consistent with the theoretical predictions for the system. This demonstration underscores that our protocol can provide an alternative way of studying thermal states physics when their direct preparation may be too difficult.
},
keywords = {UPV/EHU},
pubstate = {published},
tppubtype = {article}
}
Quantum thermalization in contemporary quantum devices, in particular quantum computers, has recently attracted significant interest. However, there are few experimental results due to the difficulty in preparing thermal states in quantum systems. In this paper, we propose a protocol to indirectly address this challenge using only pure states. While our protocol does not solve the issue of thermal state preparation, it enables the equivalent study of their dynamics. Moreover, we experimentally validate our protocol using IBM quantum devices, presenting results that demonstrate unusual relaxation in equidistant quenches. We also assess the formalism introduced for the Quantum Mpemba Effect (QME), which provides a framework for comparing the dynamics of different thermal states, we do no observe any unusual behaviour in this case, which is consistent with the theoretical predictions for the system. This demonstration underscores that our protocol can provide an alternative way of studying thermal states physics when their direct preparation may be too difficult.
Bottarelli, A.; Garcia de Andoin, M.; Chandarana, P.; Paul, K.; Chen, X.; Sanz, M.; Hauke, P.
Symmetry-enhanced counterdiabatic quantum algorithm for qudits Artículo de revista
En: 2025.
Resumen | Enlaces | BibTeX | Etiquetas: UPV/EHU
@article{nokey,
title = {Symmetry-enhanced counterdiabatic quantum algorithm for qudits},
author = {Bottarelli, A. and Garcia de Andoin, M. and Chandarana, P. and Paul, K. and Chen, X. and Sanz, M. and Hauke, P.},
url = {https://journals.aps.org/prresearch/abstract/10.1103/6ldg-3w1f},
doi = {doi.org/10.1103/6ldg-3w1f},
year = {2025},
date = {2025-10-08},
urldate = {2024-10-18},
abstract = {Qubit-based variational quantum algorithms have undergone rapid development in recent years but still face several challenges. Here, we introduce a symmetry-based enhancement to digitized counterdiabatic quantum algorithms, applicable for qudits of any dimension. This approach offers three types of compression compared to conventional variational circuits. First, compression in the circuit depth is achieved by counterdiabatic protocols. Second, information about the problem is compressed by replacing qubits with qudits, allowing for a more efficient representation of the problem. Finally, the number of parameters is reduced by employing the symmetries of the system. We illustrate this approach by tackling a graph-based optimization problem Max-3-Cut, a highly entangled state preparation, the qutrit 𝑊 state, and a two-body only antiferromagnetic Ising problem. As our numerical results show, we achieve a better convergence with a lower circuit depth and less measurement overhead, albeit with some identified limitations for which we propose a work-around. This work leads to a better design of shallow variational quantum circuits, improving the feasibility of their implementation on near-term qudit devices.},
keywords = {UPV/EHU},
pubstate = {published},
tppubtype = {article}
}
Qubit-based variational quantum algorithms have undergone rapid development in recent years but still face several challenges. Here, we introduce a symmetry-based enhancement to digitized counterdiabatic quantum algorithms, applicable for qudits of any dimension. This approach offers three types of compression compared to conventional variational circuits. First, compression in the circuit depth is achieved by counterdiabatic protocols. Second, information about the problem is compressed by replacing qubits with qudits, allowing for a more efficient representation of the problem. Finally, the number of parameters is reduced by employing the symmetries of the system. We illustrate this approach by tackling a graph-based optimization problem Max-3-Cut, a highly entangled state preparation, the qutrit 𝑊 state, and a two-body only antiferromagnetic Ising problem. As our numerical results show, we achieve a better convergence with a lower circuit depth and less measurement overhead, albeit with some identified limitations for which we propose a work-around. This work leads to a better design of shallow variational quantum circuits, improving the feasibility of their implementation on near-term qudit devices.
Becker, S.; Galke, N.; Salzmann, R.; Van Luijk, L.
Convergence Rates for the Trotter Splitting for Unbounded Operators Artículo de revista
En: Foundations of Computational Mathematics , 2025.
Resumen | Enlaces | BibTeX | Etiquetas: UAB
@article{nokey,
title = {Convergence Rates for the Trotter Splitting for Unbounded Operators},
author = {Becker, S. and Galke, N. and Salzmann, R. and Van Luijk, L.},
url = {https://link.springer.com/article/10.1007/s10208-025-09730-w},
doi = {doi.org/10.1007/s10208-025-09730-w},
year = {2025},
date = {2025-09-29},
urldate = {2024-07-04},
journal = {Foundations of Computational Mathematics },
abstract = {We study convergence rates of the Trotter splitting e^(A+L) = lim(n→∞) (e^(L/n) e^(A/n))^n in the strong operator topology. In the first part, we use complex interpolation theory to treat generators L and A of contraction semigroups on Banach spaces, with L relatively A-bounded. In the second part, we study unitary dynamics on Hilbert spaces and develop a new technique based on the concept of energy constraints. Our results provide a complete picture of the convergence rates for the Trotter splitting for all common types of Schrödinger and Dirac operators, including singular, confining and magnetic vector potentials, as well as molecular many-body Hamiltonians in dimension d = 3. Using the Brezis-Mironescu inequality, we derive convergence rates for the Schrödinger operator with V(x) = ±|x|^(-a) potential. In each case, our conditions are fully explicit.},
keywords = {UAB},
pubstate = {published},
tppubtype = {article}
}
We study convergence rates of the Trotter splitting e^(A+L) = lim(n→∞) (e^(L/n) e^(A/n))^n in the strong operator topology. In the first part, we use complex interpolation theory to treat generators L and A of contraction semigroups on Banach spaces, with L relatively A-bounded. In the second part, we study unitary dynamics on Hilbert spaces and develop a new technique based on the concept of energy constraints. Our results provide a complete picture of the convergence rates for the Trotter splitting for all common types of Schrödinger and Dirac operators, including singular, confining and magnetic vector potentials, as well as molecular many-body Hamiltonians in dimension d = 3. Using the Brezis-Mironescu inequality, we derive convergence rates for the Schrödinger operator with V(x) = ±|x|^(-a) potential. In each case, our conditions are fully explicit.
Fontana, P.; Miranda Riaza, M.; Celi, A.
Efficient Finite-Resource Formulation of Non-Abelian Lattice Gauge Theories beyond One Dimension Artículo de revista
En: 2025.
Resumen | Enlaces | BibTeX | Etiquetas: UAB
@article{nokey,
title = {Efficient Finite-Resource Formulation of Non-Abelian Lattice Gauge Theories beyond One Dimension},
author = {Fontana, P. and Miranda Riaza, M. and Celi, A.},
url = {https://journals.aps.org/prx/abstract/10.1103/k9p6-c649},
doi = {doi.org/10.1103/k9p6-c649},
year = {2025},
date = {2025-09-09},
urldate = {2025-09-09},
abstract = {Non-Abelian gauge theories provide the most accurate description of fundamental interactions, showing remarkable agreement with experimental data in cosmology and particle physics. Highly precise predictions can be made using standard techniques, both in the continuum and in the lattice frameworks. However, classical methods have limitations, particularly when attempting to extrapolate the continuum limit from the study of lattice gauge theories. Complementing classical computations or combining them with quantum computational methods, to improve the predictions toward the continuum limit with current quantum resources, is a formidable open challenge. In this paper, we propose a resource-efficient method to compute the running of the coupling in non-Abelian gauge theories beyond one spatial dimension. We first represent the Hamiltonian on periodic lattices in terms of loop variables and conjugate loop electric fields, exploiting the Gauss law to retain the gauge-independent ones. Then, we identify a local basis for small and large loops variationally to minimize the truncation error while computing the running of the coupling on small tori. Our method enables computations at arbitrary values of the bare coupling and lattice spacing with current quantum computers, simulators, and tensor-network calculations, in regimes otherwise inaccessible.},
keywords = {UAB},
pubstate = {published},
tppubtype = {article}
}
Non-Abelian gauge theories provide the most accurate description of fundamental interactions, showing remarkable agreement with experimental data in cosmology and particle physics. Highly precise predictions can be made using standard techniques, both in the continuum and in the lattice frameworks. However, classical methods have limitations, particularly when attempting to extrapolate the continuum limit from the study of lattice gauge theories. Complementing classical computations or combining them with quantum computational methods, to improve the predictions toward the continuum limit with current quantum resources, is a formidable open challenge. In this paper, we propose a resource-efficient method to compute the running of the coupling in non-Abelian gauge theories beyond one spatial dimension. We first represent the Hamiltonian on periodic lattices in terms of loop variables and conjugate loop electric fields, exploiting the Gauss law to retain the gauge-independent ones. Then, we identify a local basis for small and large loops variationally to minimize the truncation error while computing the running of the coupling on small tori. Our method enables computations at arbitrary values of the bare coupling and lattice spacing with current quantum computers, simulators, and tensor-network calculations, in regimes otherwise inaccessible.
Ruiz, R.; Sopena, A.; Pozsgay, B.; López, E.
Efficient Eigenstate Preparation in an Integrable Model with Hilbert Space Fragmentation Artículo de revista
En: 2025.
Resumen | Enlaces | BibTeX | Etiquetas: CSIC-4.7
@article{nokey,
title = {Efficient Eigenstate Preparation in an Integrable Model with Hilbert Space Fragmentation},
author = {Ruiz, R. and Sopena, A. and Pozsgay, B. and López, E. },
url = {https://journals.aps.org/prxquantum/abstract/10.1103/g9f9-p8ks},
doi = {doi.org/10.1103/g9f9-p8ks},
year = {2025},
date = {2025-07-30},
urldate = {2024-12-03},
abstract = {We consider the preparation of all the eigenstates of spin chains using quantum circuits. It is known that generic eigenstates of free-fermionic spin chains can be prepared with circuits whose depth grows only polynomially with the length of the chain and the number of particles. We show that the polynomial growth is also achievable for selected interacting models where the interaction between the particles is sufficiently simple. Our working example is the folded XXZ model, an integrable spin chain that exhibits Hilbert space fragmentation. We present the explicit quantum circuits that prepare arbitrary eigenstates of this model on an open chain efficiently. We perform error-mitigated noisy simulations with circuits of up to 13 qubits and different connectivities between qubits, achieving a relative error below 5%. As a byproduct, we extend a recent reformulation of the Bethe ansatz as a quantum circuit from closed to open boundary conditions.},
keywords = {CSIC-4.7},
pubstate = {published},
tppubtype = {article}
}
We consider the preparation of all the eigenstates of spin chains using quantum circuits. It is known that generic eigenstates of free-fermionic spin chains can be prepared with circuits whose depth grows only polynomially with the length of the chain and the number of particles. We show that the polynomial growth is also achievable for selected interacting models where the interaction between the particles is sufficiently simple. Our working example is the folded XXZ model, an integrable spin chain that exhibits Hilbert space fragmentation. We present the explicit quantum circuits that prepare arbitrary eigenstates of this model on an open chain efficiently. We perform error-mitigated noisy simulations with circuits of up to 13 qubits and different connectivities between qubits, achieving a relative error below 5%. As a byproduct, we extend a recent reformulation of the Bethe ansatz as a quantum circuit from closed to open boundary conditions.
Ding, Y.; Ban, Y.; Sanz, M.; Martín-Guerrero, J. D.; Chen, X.
Quantum Active Learning Artículo de revista
En: Physical Review A, 2025.
Resumen | Enlaces | BibTeX | Etiquetas: UPV/EHU
@article{nokey,
title = {Quantum Active Learning},
author = {Ding, Y. and Ban, Y. and Sanz, M. and Martín-Guerrero, J.D. and Chen, X. },
url = {https://journals.aps.org/pra/abstract/10.1103/c8q9-6vy7},
doi = {doi.org/10.1103/c8q9-6vy7},
year = {2025},
date = {2025-07-10},
urldate = {2024-05-28},
journal = {Physical Review A},
abstract = {Quantum machine learning (QML), as an extension of classical machine learning that harnesses quantum mechanics, facilitates efficient learning from data encoded in quantum states. Training a quantum neural network (QNN) typically demands a substantial labeled training set for supervised learning. Human annotators, often experts, provide labels for samples through additional experiments, adding to the training cost. To mitigate this expense, there is a quest for methods that maintain model performance over fully labeled data sets while requiring fewer labeled samples in practice, thereby extending few-shot learning to the quantum realm. Quantum active learning (QAL) estimates the uncertainty of quantum data to select the most informative samples from a pool for labeling. Consequently, a QML model is supposed to accumulate maximal knowledge as the training set comprises labeled samples selected via sampling strategies. Notably, the QML models trained within the QAL framework are not restricted to specific types, allowing performance enhancement from the model architecture's perspective towards few-shot learning. Recognizing symmetry as a fundamental concept in physics ubiquitous across various domains, we leverage the symmetry inherent in quantum states induced by the embedding of classical data for model design. We employ an equivariant QNN capable of generalizing from fewer data with geometric priors. We benchmark the performance of QAL on two classification problems, observing both positive and negative results. QAL effectively trains the model, achieving performance comparable to that on fully labeled data sets by labeling less than 7% of the samples in the pool with unbiased sampling behavior. Furthermore, we elucidate the negative result of QAL being overtaken by random sampling baseline through miscellaneous numerical experiments. Our work lays the groundwork for real-world applications of QML by addressing realistic experimental costs.},
keywords = {UPV/EHU},
pubstate = {published},
tppubtype = {article}
}
Quantum machine learning (QML), as an extension of classical machine learning that harnesses quantum mechanics, facilitates efficient learning from data encoded in quantum states. Training a quantum neural network (QNN) typically demands a substantial labeled training set for supervised learning. Human annotators, often experts, provide labels for samples through additional experiments, adding to the training cost. To mitigate this expense, there is a quest for methods that maintain model performance over fully labeled data sets while requiring fewer labeled samples in practice, thereby extending few-shot learning to the quantum realm. Quantum active learning (QAL) estimates the uncertainty of quantum data to select the most informative samples from a pool for labeling. Consequently, a QML model is supposed to accumulate maximal knowledge as the training set comprises labeled samples selected via sampling strategies. Notably, the QML models trained within the QAL framework are not restricted to specific types, allowing performance enhancement from the model architecture's perspective towards few-shot learning. Recognizing symmetry as a fundamental concept in physics ubiquitous across various domains, we leverage the symmetry inherent in quantum states induced by the embedding of classical data for model design. We employ an equivariant QNN capable of generalizing from fewer data with geometric priors. We benchmark the performance of QAL on two classification problems, observing both positive and negative results. QAL effectively trains the model, achieving performance comparable to that on fully labeled data sets by labeling less than 7% of the samples in the pool with unbiased sampling behavior. Furthermore, we elucidate the negative result of QAL being overtaken by random sampling baseline through miscellaneous numerical experiments. Our work lays the groundwork for real-world applications of QML by addressing realistic experimental costs.
Olivera-Atencio, M. L.; Lamata, L.; Casado-Pascual, J.
Impact of amplitude and phase damping noise on quantum reinforcement learning: challenges and opportunities Artículo de revista
En: The European Physical Journal Special Topics (EPJ ST), 2025.
Resumen | Enlaces | BibTeX | Etiquetas: US
@article{nokey,
title = {Impact of amplitude and phase damping noise on quantum reinforcement learning: challenges and opportunities},
author = {Olivera-Atencio, M.L. and Lamata, L. and Casado-Pascual, J.},
editor = {Olivera-Atencio, M.L. and Lamata, L. and Casado-Pascual, J. },
url = {https://link.springer.com/article/10.1140/epjs/s11734-025-01760-3},
doi = {doi.org/10.1140/epjs/s11734-025-01760-3},
year = {2025},
date = {2025-07-04},
urldate = {2025-07-04},
journal = {The European Physical Journal Special Topics (EPJ ST)},
abstract = {Quantum machine learning (QML) is an emerging field with significant potential, yet it remains highly susceptible to noise, which poses a major challenge to its practical implementation. While various noise mitigation strategies have been proposed to enhance algorithmic performance, the impact of noise is not fully understood. In this work, we investigate the effects of amplitude and phase damping noise on a quantum reinforcement learning algorithm. Through analytical and numerical analysis, we assess how these noise sources influence the learning process and overall performance. Our findings contribute to a deeper understanding of the role of noise in quantum learning algorithms and suggest that, rather than being purely detrimental, unavoidable noise may present opportunities to enhance QML processes.},
keywords = {US},
pubstate = {published},
tppubtype = {article}
}
Quantum machine learning (QML) is an emerging field with significant potential, yet it remains highly susceptible to noise, which poses a major challenge to its practical implementation. While various noise mitigation strategies have been proposed to enhance algorithmic performance, the impact of noise is not fully understood. In this work, we investigate the effects of amplitude and phase damping noise on a quantum reinforcement learning algorithm. Through analytical and numerical analysis, we assess how these noise sources influence the learning process and overall performance. Our findings contribute to a deeper understanding of the role of noise in quantum learning algorithms and suggest that, rather than being purely detrimental, unavoidable noise may present opportunities to enhance QML processes.
Dastbasteh, R.; Etxezarreta Martinez, J.; A. deMarti iOlius Nemec, A. Crespo Bofill.
An Infinite class of quantum codes derived from duadic constacyclic codes Artículo de revista
En: Quantum Information Processing, 2025.
Resumen | Enlaces | BibTeX | Etiquetas: TECNUN
@article{nokey,
title = {An Infinite class of quantum codes derived from duadic constacyclic codes},
author = {Dastbasteh, R. and Etxezarreta Martinez, J. and Nemec, A. deMarti iOlius, A. Crespo Bofill.},
url = {https://link.springer.com/article/10.1007/s11128-025-04828-0},
doi = {doi.org/10.1007/s11128-025-04828-0},
year = {2025},
date = {2025-07-03},
urldate = {2024-05-27},
journal = {Quantum Information Processing},
abstract = {We present a family of quantum stabilizer codes using the structure of duadic constacyclic codes over F4. Within this family, quantum codes can possess varying dimensions, and their minimum distances are lower bounded by a square root bound. For each fixed dimension, this allows us to construct an infinite sequence of binary quantum codes with a growing minimum distance. Additionally, we prove that this family of quantum codes includes an infinite subclass of degenerate codes. We also introduce a technique for extending splittings of duadic constacyclic codes, providing new insights into the minimum distance and minimum odd-like weight of specific duadic constacyclic codes. Finally, we provide numerical examples of some quantum codes with short lengths within this family.},
howpublished = {Preprint},
keywords = {TECNUN},
pubstate = {published},
tppubtype = {article}
}
We present a family of quantum stabilizer codes using the structure of duadic constacyclic codes over F4. Within this family, quantum codes can possess varying dimensions, and their minimum distances are lower bounded by a square root bound. For each fixed dimension, this allows us to construct an infinite sequence of binary quantum codes with a growing minimum distance. Additionally, we prove that this family of quantum codes includes an infinite subclass of degenerate codes. We also introduce a technique for extending splittings of duadic constacyclic codes, providing new insights into the minimum distance and minimum odd-like weight of specific duadic constacyclic codes. Finally, we provide numerical examples of some quantum codes with short lengths within this family.
Bou-Comas, A.; Płodzień, M.; Tagliacozzo, L.; García-Ripoll, J. J.
Quantics Tensor Train for solving Gross-Pitaevskii equation Working paper
2025.
Resumen | Enlaces | BibTeX | Etiquetas: CSIC-4.7
@workingpaper{nokey,
title = {Quantics Tensor Train for solving Gross-Pitaevskii equation},
author = {Bou-Comas, A. and Płodzień, M. and Tagliacozzo, L. and García-Ripoll, J.J.},
url = {https://arxiv.org/abs/2507.03134},
doi = {doi.org/10.48550/arXiv.2507.03134},
year = {2025},
date = {2025-07-03},
abstract = {We present a quantum-inspired solver for the one-dimensional Gross-Pitaevskii equation in the Quantics Tensor-Train (QTT) representation. By evolving the system entirely within a low-rank tensor manifold, the method sidesteps the memory and runtime barriers that limit conventional finite-difference and spectral schemes. Two complementary algorithms are developed: an imaginary-time projector that drives the condensate toward its variational ground state and a rank-adapted fourth-order Runge-Kutta integrator for real-time dynamics. The framework captures a broad range of physical scenarios - including barrier-confined condensates, quasi-random potentials, long-range dipolar interactions, and multicomponent spinor dynamics - without leaving the compressed representation. Relative to standard discretizations, the QTT approach achieves an exponential reduction in computational resources while retaining quantitative accuracy, thereby extending the practicable regime of Gross-Pitaevskii simulations on classical hardware. These results position tensor networks as a practical bridge between high-performance classical computing and prospective quantum hardware for the numerical treatment of nonlinear Schrodinger-type partial differential equations.},
keywords = {CSIC-4.7},
pubstate = {published},
tppubtype = {workingpaper}
}
We present a quantum-inspired solver for the one-dimensional Gross-Pitaevskii equation in the Quantics Tensor-Train (QTT) representation. By evolving the system entirely within a low-rank tensor manifold, the method sidesteps the memory and runtime barriers that limit conventional finite-difference and spectral schemes. Two complementary algorithms are developed: an imaginary-time projector that drives the condensate toward its variational ground state and a rank-adapted fourth-order Runge-Kutta integrator for real-time dynamics. The framework captures a broad range of physical scenarios - including barrier-confined condensates, quasi-random potentials, long-range dipolar interactions, and multicomponent spinor dynamics - without leaving the compressed representation. Relative to standard discretizations, the QTT approach achieves an exponential reduction in computational resources while retaining quantitative accuracy, thereby extending the practicable regime of Gross-Pitaevskii simulations on classical hardware. These results position tensor networks as a practical bridge between high-performance classical computing and prospective quantum hardware for the numerical treatment of nonlinear Schrodinger-type partial differential equations.
Labay-Mora, A.; Fiorelli, E.; Zambrini, R.; Giorgi, G. L.
Theoretical framework for quantum associative memories Artículo de revista
En: 2025.
Resumen | Enlaces | BibTeX | Etiquetas: CSIC-4.7
@article{nokey,
title = {Theoretical framework for quantum associative memories},
author = {Labay-Mora, A. and Fiorelli, E. and Zambrini, R. and Giorgi, G.L. },
url = {https://iopscience.iop.org/article/10.1088/2058-9565/ade184},
doi = {10.1088/2058-9565/ade184 },
year = {2025},
date = {2025-07-02},
urldate = {2025-07-02},
abstract = {Associative memory (AM) refers to the ability to relate a memory with an input and targets the restoration of corrupted patterns. It has been intensively studied in classical physical systems, as in neural networks where an attractor dynamics settles on stable solutions. Several extensions to the quantum domain have been recently reported, displaying different features. In this work, we develop a comprehensive framework for a quantum AM (QAM) based on open quantum system dynamics, which allows us to compare existing models, identify the theoretical prerequisites for performing AM tasks, and extend it in different forms. The map that achieves an exponential increase in the number of stored patterns with respect to classical systems is derived. We establish the crucial role of symmetries and dissipation in the operation of QAM. Our theoretical analysis demonstrates the feasibility of addressing both quantum and classical patterns, orthogonal and non-orthogonal memories, stationary and metastable operating regimes, and measurement-based outputs. Finally, this opens up new avenues for practical applications in quantum computing and machine learning, such as quantum error correction or quantum memories.
},
howpublished = {Quantum Science and Technology - IOP},
keywords = {CSIC-4.7},
pubstate = {published},
tppubtype = {article}
}
Associative memory (AM) refers to the ability to relate a memory with an input and targets the restoration of corrupted patterns. It has been intensively studied in classical physical systems, as in neural networks where an attractor dynamics settles on stable solutions. Several extensions to the quantum domain have been recently reported, displaying different features. In this work, we develop a comprehensive framework for a quantum AM (QAM) based on open quantum system dynamics, which allows us to compare existing models, identify the theoretical prerequisites for performing AM tasks, and extend it in different forms. The map that achieves an exponential increase in the number of stored patterns with respect to classical systems is derived. We establish the crucial role of symmetries and dissipation in the operation of QAM. Our theoretical analysis demonstrates the feasibility of addressing both quantum and classical patterns, orthogonal and non-orthogonal memories, stationary and metastable operating regimes, and measurement-based outputs. Finally, this opens up new avenues for practical applications in quantum computing and machine learning, such as quantum error correction or quantum memories.
Berardini, E.; Dastbasteh, R.; Etxezarreta Martinez, J.; Jain, S.; Sanz Larrarte, O.
Asymptotically good CSS-T codes and a new construction of triorthogonal codes Artículo de revista
En: IEEE Journal on Selected Areas in Information Theory, 2025.
Resumen | Enlaces | BibTeX | Etiquetas: TECNUN
@article{nokey,
title = {Asymptotically good CSS-T codes and a new construction of triorthogonal codes},
author = {Berardini, E. and Dastbasteh, R. and Etxezarreta Martinez, J. and Jain, S. and Sanz Larrarte, O. },
url = {https://arxiv.org/abs/2412.08586},
doi = {10.1109/JSAIT.2025.3582156},
year = {2025},
date = {2025-06-20},
journal = {IEEE Journal on Selected Areas in Information Theory},
abstract = {We propose a new systematic construction of CSS-T codes from any given CSS code using a map ϕ. When ϕ is the identity map I, we retrieve the construction of hu2021mitigating and use it to prove the existence of asymptotically good binary CSS-T codes, resolving a previously open problem in the literature, and of asymptotically good quantum LDPC CSS-T codes. We analyze the structure of the logical operators corresponding to certain non-Clifford gates supported by the quantum codes obtained from this construction (ϕ=I), concluding that they always result in the logical identity. An immediate application of these codes in dealing with coherent noise is discussed. We then develop a new doubling transformation for obtaining triorthogonal codes, which generalizes the doubling construction presented in jain2024. Our approach permits using self-orthogonal codes, instead of only doubly-even codes, as building blocks for triorthogonal codes. This broadens the range of codes available for magic state distillation.},
keywords = {TECNUN},
pubstate = {published},
tppubtype = {article}
}
We propose a new systematic construction of CSS-T codes from any given CSS code using a map ϕ. When ϕ is the identity map I, we retrieve the construction of hu2021mitigating and use it to prove the existence of asymptotically good binary CSS-T codes, resolving a previously open problem in the literature, and of asymptotically good quantum LDPC CSS-T codes. We analyze the structure of the logical operators corresponding to certain non-Clifford gates supported by the quantum codes obtained from this construction (ϕ=I), concluding that they always result in the logical identity. An immediate application of these codes in dealing with coherent noise is discussed. We then develop a new doubling transformation for obtaining triorthogonal codes, which generalizes the doubling construction presented in jain2024. Our approach permits using self-orthogonal codes, instead of only doubly-even codes, as building blocks for triorthogonal codes. This broadens the range of codes available for magic state distillation.
Rodriguez-Grasa, P.; Ban, Y.; Sanz, M.
Neural quantum kernels: Training quantum kernels with quantum neural networks Artículo de revista
En: Physical Review Research, vol. 7, iss. 2, no 23269 , 2025.
Resumen | Enlaces | BibTeX | Etiquetas: UPV/EHU
@article{nokey,
title = {Neural quantum kernels: Training quantum kernels with quantum neural networks},
author = {Rodriguez-Grasa, P. and Ban, Y. and Sanz, M.},
url = {https://journals.aps.org/prresearch/abstract/10.1103/xphb-x2g4},
doi = {doi.org/10.1103/xphb-x2g4},
year = {2025},
date = {2025-06-16},
urldate = {2025-06-16},
journal = {Physical Review Research},
volume = {7},
number = {23269 },
issue = {2},
abstract = {Quantum and classical machine learning have been naturally connected through kernel methods, which have also served as proof-of-concept for quantum advantage. Quantum embeddings encode classical data into quantum feature states, enabling the construction of embedding quantum kernels (EQKs) by measuring vector similarities and projected quantum kernels (PQKs) through projections of these states. However, in both approaches, the model is influenced by the choice of the embedding. In this work, we propose using the training of a quantum neural network (QNN) to construct neural quantum kernels, specifically neural EQKs and neural PQKs—problem-inspired kernel functions. Unlike previous approaches, our method requires the kernel matrix to be constructed only once, significantly reducing computational overhead. To achieve this, we introduce a scalable training method for an 𝑛-qubit data reuploading QNN. Furthermore, we demonstrate neural quantum kernels can alleviate exponential concentration and enhance generalization capabilities compared to problem-agnostic kernels, positioning them as a scalable and robust solution for quantum machine learning applications.},
keywords = {UPV/EHU},
pubstate = {published},
tppubtype = {article}
}
Quantum and classical machine learning have been naturally connected through kernel methods, which have also served as proof-of-concept for quantum advantage. Quantum embeddings encode classical data into quantum feature states, enabling the construction of embedding quantum kernels (EQKs) by measuring vector similarities and projected quantum kernels (PQKs) through projections of these states. However, in both approaches, the model is influenced by the choice of the embedding. In this work, we propose using the training of a quantum neural network (QNN) to construct neural quantum kernels, specifically neural EQKs and neural PQKs—problem-inspired kernel functions. Unlike previous approaches, our method requires the kernel matrix to be constructed only once, significantly reducing computational overhead. To achieve this, we introduce a scalable training method for an 𝑛-qubit data reuploading QNN. Furthermore, we demonstrate neural quantum kernels can alleviate exponential concentration and enhance generalization capabilities compared to problem-agnostic kernels, positioning them as a scalable and robust solution for quantum machine learning applications.
Ruiz, R.; Sopena, A.; López, E.; Sierra, G.; Pozsgay, B.
Bethe Ansatz, quantum circuits, and the F-basis Artículo de revista
En: SciPost Physics, vol. 18, pp. 187, 2025.
Resumen | Enlaces | BibTeX | Etiquetas: CSIC-4.7
@article{nokey,
title = {Bethe Ansatz, quantum circuits, and the F-basis},
author = {Ruiz, R. and Sopena, A. and López, E. and Sierra, G. and Pozsgay, B. },
url = {https://scipost.org/SciPostPhys.18.6.187},
doi = {doi: 10.21468/SciPostPhys.18.6.187},
year = {2025},
date = {2025-06-12},
journal = {SciPost Physics},
volume = {18},
pages = {187},
abstract = {The Bethe Ansatz is a method for constructing exact eigenstates of quantum-integrable spin chains. Recently, deterministic quantum algorithms, referred to as "algebraic Bethe circuits", have been developed to prepare Bethe states for the spin-1/2 XXZ model. These circuits represent a unitary formulation of the standard algebraic Bethe Ansatz, expressed using matrix-product states that act on both the spin chain and an auxiliary space. In this work, we systematize these previous results, and show that algebraic Bethe circuits can be derived by a change of basis in the auxiliary space. The new basis, identical to the "F-basis" known from the theory of quantum-integrable models, generates the linear superposition of plane waves that is characteristic of the coordinate Bethe Ansatz. We explain this connection, highlighting that certain properties of the F-basis (namely, the exchange symmetry of the spins) are crucial for the construction of algebraic Bethe circuits. We demonstrate our approach by presenting new quantum circuits for the inhomogeneous spin-1/2 XXZ model.},
keywords = {CSIC-4.7},
pubstate = {published},
tppubtype = {article}
}
The Bethe Ansatz is a method for constructing exact eigenstates of quantum-integrable spin chains. Recently, deterministic quantum algorithms, referred to as "algebraic Bethe circuits", have been developed to prepare Bethe states for the spin-1/2 XXZ model. These circuits represent a unitary formulation of the standard algebraic Bethe Ansatz, expressed using matrix-product states that act on both the spin chain and an auxiliary space. In this work, we systematize these previous results, and show that algebraic Bethe circuits can be derived by a change of basis in the auxiliary space. The new basis, identical to the "F-basis" known from the theory of quantum-integrable models, generates the linear superposition of plane waves that is characteristic of the coordinate Bethe Ansatz. We explain this connection, highlighting that certain properties of the F-basis (namely, the exchange symmetry of the spins) are crucial for the construction of algebraic Bethe circuits. We demonstrate our approach by presenting new quantum circuits for the inhomogeneous spin-1/2 XXZ model.
Gonzalez-Conde, J.; Lewis, D.; Bharadwaj, S. S.; Sanz, M.
Quantum Carleman linearization efficiency in nonlinear fluid dynamics Artículo de revista
En: Physical Review Research, vol. 7, iss. 2, no 23254, 2025.
Resumen | Enlaces | BibTeX | Etiquetas: UPV/EHU
@article{nokey,
title = {Quantum Carleman linearization efficiency in nonlinear fluid dynamics},
author = {Gonzalez-Conde, J. and Lewis, D. and Bharadwaj, S.S. and Sanz, M. },
url = {https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.7.023254},
doi = {doi.org/10.1103/PhysRevResearch.7.023254},
year = {2025},
date = {2025-06-12},
urldate = {2025-06-12},
journal = {Physical Review Research},
volume = {7},
number = {23254},
issue = {2},
abstract = {Computational fluid dynamics (CFD) is a specialized branch of fluid mechanics that utilizes numerical methods and algorithms to solve and analyze fluid-flow problems. One promising avenue to enhance CFD is the use of quantum computing, which has the potential to resolve nonlinear differential equations more efficiently than classical computers. Here, we try to answer the question of which regimes of nonlinear partial differential equations for fluid dynamics can have an efficient quantum algorithm. We propose a connection between the numerical parameter 𝑅, which guarantees efficiency in the truncation of the Carleman linearization, and the physical parameters that describe the fluid flow. This link can be made thanks to the Kolmogorov scale, which determines the minimum size of the grid needed to properly resolve the energy cascade induced by the nonlinear term. Additionally, we introduce the formalism for vector field simulation in different spatial dimensions, providing the discretization of the operators and the boundary conditions.},
keywords = {UPV/EHU},
pubstate = {published},
tppubtype = {article}
}
Computational fluid dynamics (CFD) is a specialized branch of fluid mechanics that utilizes numerical methods and algorithms to solve and analyze fluid-flow problems. One promising avenue to enhance CFD is the use of quantum computing, which has the potential to resolve nonlinear differential equations more efficiently than classical computers. Here, we try to answer the question of which regimes of nonlinear partial differential equations for fluid dynamics can have an efficient quantum algorithm. We propose a connection between the numerical parameter 𝑅, which guarantees efficiency in the truncation of the Carleman linearization, and the physical parameters that describe the fluid flow. This link can be made thanks to the Kolmogorov scale, which determines the minimum size of the grid needed to properly resolve the energy cascade induced by the nonlinear term. Additionally, we introduce the formalism for vector field simulation in different spatial dimensions, providing the discretization of the operators and the boundary conditions.
Farreras, M.; Cervera-Lierta, A.
Simulation of the 1d XY model on a quantum computer Artículo de revista
En: SciPost Physics Lecture Notes, 2025.
Resumen | Enlaces | BibTeX | Etiquetas: BSC
@article{nokey,
title = {Simulation of the 1d XY model on a quantum computer},
author = {Farreras, M. and Cervera-Lierta, A.},
url = {https://scipost.org/10.21468/SciPostPhysLectNotes.95},
doi = {10.21468/SciPostPhysLectNotes.95},
year = {2025},
date = {2025-06-11},
urldate = {2024-10-28},
journal = {SciPost Physics Lecture Notes},
abstract = {The field of quantum computing has grown rapidly in recent years, both in terms of theoretical advancements and the practical construction of quantum computers. These computers were initially proposed, among other reasons, to efficiently simulate and understand the complexities of quantum physics.
In this paper, we present a comprehensive scheme for the exact simulation of the one-dimensional (1-D) XY model on a quantum computer. We successfully diagonalize the proposed Hamiltonian, enabling access to the complete energy spectrum. Furthermore, we propose a novel approach for designing a quantum circuit that performs exact time evolution.
Among the applications enabled by this approach, we compute the ground- and excited-state energies of the symmetric XY model for spin chains with n=4 and n=8 spins. In addition, we calculate the expected value of the transverse magnetization in the ground state of the transverse Ising model. Both studies reveal a quantum phase transition from an antiferromagnetic to a paramagnetic state.
Finally, we simulate the time evolution of the all-spins-up state in the transverse Ising model. The scalability and high performance of our algorithm make it an ideal candidate for benchmarking quantum computers while also providing a foundation for simulating other integrable models on quantum computing platforms.},
keywords = {BSC},
pubstate = {published},
tppubtype = {article}
}
The field of quantum computing has grown rapidly in recent years, both in terms of theoretical advancements and the practical construction of quantum computers. These computers were initially proposed, among other reasons, to efficiently simulate and understand the complexities of quantum physics.
In this paper, we present a comprehensive scheme for the exact simulation of the one-dimensional (1-D) XY model on a quantum computer. We successfully diagonalize the proposed Hamiltonian, enabling access to the complete energy spectrum. Furthermore, we propose a novel approach for designing a quantum circuit that performs exact time evolution.
Among the applications enabled by this approach, we compute the ground- and excited-state energies of the symmetric XY model for spin chains with n=4 and n=8 spins. In addition, we calculate the expected value of the transverse magnetization in the ground state of the transverse Ising model. Both studies reveal a quantum phase transition from an antiferromagnetic to a paramagnetic state.
Finally, we simulate the time evolution of the all-spins-up state in the transverse Ising model. The scalability and high performance of our algorithm make it an ideal candidate for benchmarking quantum computers while also providing a foundation for simulating other integrable models on quantum computing platforms.
In this paper, we present a comprehensive scheme for the exact simulation of the one-dimensional (1-D) XY model on a quantum computer. We successfully diagonalize the proposed Hamiltonian, enabling access to the complete energy spectrum. Furthermore, we propose a novel approach for designing a quantum circuit that performs exact time evolution.
Among the applications enabled by this approach, we compute the ground- and excited-state energies of the symmetric XY model for spin chains with n=4 and n=8 spins. In addition, we calculate the expected value of the transverse magnetization in the ground state of the transverse Ising model. Both studies reveal a quantum phase transition from an antiferromagnetic to a paramagnetic state.
Finally, we simulate the time evolution of the all-spins-up state in the transverse Ising model. The scalability and high performance of our algorithm make it an ideal candidate for benchmarking quantum computers while also providing a foundation for simulating other integrable models on quantum computing platforms.
Edmunds, C. L.; Rico, E.; Arrazola, I.; Brennen, G. K.; Meth, M.; Blatt, R.; Ringbauer, M.
Symmetry-Protected Topological Haldane Phase on a Qudit Quantum Processor Working paper
2025.
Resumen | Enlaces | BibTeX | Etiquetas: CSIC-4.7
@workingpaper{nokey,
title = {Symmetry-Protected Topological Haldane Phase on a Qudit Quantum Processor},
author = {Edmunds, C. L. . and Rico, E. and Arrazola, I. and Brennen, G. K. and Meth, M. and Blatt, R. and Ringbauer, M.},
url = {https://journals.aps.org/prxquantum/abstract/10.1103/PRXQuantum.6.020349},
doi = {doi.org/10.1103/PRXQuantum.6.020349},
year = {2025},
date = {2025-06-11},
urldate = {2025-08-08},
abstract = {Symmetry-protected topological phases have fundamentally changed our understanding of quantum matter. An archetypal example of such a quantum phase of matter is the Haldane phase, containing the spin-1 Heisenberg chain. The intrinsic quantum nature of such phases, however, often makes it challenging to study them using classical means. Here, we use trapped-ion qutrits to natively engineer spin-1 chains within the Haldane phase. Using a scalable deterministic procedure to prepare the Affleck-Kennedy-Lieb-Tasaki (AKLT) state within the Haldane phase, we study the topological features of this system on a qudit quantum processor. Notably, we verify the long-range string order of the state, despite its short-range correlations, and observe spin fractionalization of the physical spin-1 particles into effective qubits at the chain edges, a defining feature of this system. The native realization of Haldane physics on a qudit quantum processor and the scalable preparation procedures open the door to the efficient exploration of a wide range of systems beyond spin-1/2.},
keywords = {CSIC-4.7},
pubstate = {published},
tppubtype = {workingpaper}
}
Symmetry-protected topological phases have fundamentally changed our understanding of quantum matter. An archetypal example of such a quantum phase of matter is the Haldane phase, containing the spin-1 Heisenberg chain. The intrinsic quantum nature of such phases, however, often makes it challenging to study them using classical means. Here, we use trapped-ion qutrits to natively engineer spin-1 chains within the Haldane phase. Using a scalable deterministic procedure to prepare the Affleck-Kennedy-Lieb-Tasaki (AKLT) state within the Haldane phase, we study the topological features of this system on a qudit quantum processor. Notably, we verify the long-range string order of the state, despite its short-range correlations, and observe spin fractionalization of the physical spin-1 particles into effective qubits at the chain edges, a defining feature of this system. The native realization of Haldane physics on a qudit quantum processor and the scalable preparation procedures open the door to the efficient exploration of a wide range of systems beyond spin-1/2.
García-Beni, J.; Paparelle, I.; Parigi, V.; Giorgi, G. L.; Soriano, M. C.; Zambrini, R.
Quantum machine learning via continuous-variable cluster states and teleportation Artículo de revista
En: EPJ Quantum Technology, vol. 12, iss. 1, no 63, 2025.
Resumen | Enlaces | BibTeX | Etiquetas: UIB
@article{nokey,
title = {Quantum machine learning via continuous-variable cluster states and teleportation},
author = {García-Beni, J. and Paparelle, I. and Parigi, V. and Giorgi, G.L. and Soriano, M.C. and Zambrini, R.},
url = {https://epjquantumtechnology.springeropen.com/articles/10.1140/epjqt/s40507-025-00352-3},
doi = {doi.org/10.1140/epjqt/s40507-025-00352-3},
year = {2025},
date = {2025-06-02},
journal = {EPJ Quantum Technology},
volume = {12},
number = {63},
issue = {1},
abstract = {We propose a new approach for a photonic platform suitable for distributed quantum machine learning and exhibiting memory. This measurement-based quantum reservoir computing takes advantage of continuous variable cluster states as the main quantum resource. Cluster states are key to several photonic quantum technologies, enabling universal quantum computing as well as quantum communication protocols. The proposed measurement-based quantum reservoir computing is based on a neural network of cluster states and local operations, where input data are encoded through measurement, thanks to quantum teleportation. In this design, measurements enable input injections, information processing and continuous monitoring for time series processing. The architecture’s power and versatility are tested by performing a set of benchmark tasks showing that the protocol displays internal memory and is suitable for both static and temporal information processing without hardware modifications. This design opens the way to distributed machine learning.},
keywords = {UIB},
pubstate = {published},
tppubtype = {article}
}
We propose a new approach for a photonic platform suitable for distributed quantum machine learning and exhibiting memory. This measurement-based quantum reservoir computing takes advantage of continuous variable cluster states as the main quantum resource. Cluster states are key to several photonic quantum technologies, enabling universal quantum computing as well as quantum communication protocols. The proposed measurement-based quantum reservoir computing is based on a neural network of cluster states and local operations, where input data are encoded through measurement, thanks to quantum teleportation. In this design, measurements enable input injections, information processing and continuous monitoring for time series processing. The architecture’s power and versatility are tested by performing a set of benchmark tasks showing that the protocol displays internal memory and is suitable for both static and temporal information processing without hardware modifications. This design opens the way to distributed machine learning.
H.C., Zhang; Sierra, G.
Kramers-Wannier self-duality and non-invertible translation symmetry in quantum chains: a wave-function perspective Artículo de revista
En: Journal of High Energy Physics (JHEP), 2025.
Resumen | Enlaces | BibTeX | Etiquetas: CSIC-4.7
@article{nokey,
title = {Kramers-Wannier self-duality and non-invertible translation symmetry in quantum chains: a wave-function perspective},
author = {Zhang H.C. and Sierra, G. },
url = {https://link.springer.com/article/10.1007/JHEP05(2025)157},
doi = {doi.org/10.1007/JHEP05(2025)157},
year = {2025},
date = {2025-05-20},
urldate = {2025-05-20},
journal = {Journal of High Energy Physics (JHEP)},
abstract = {The Kramers-Wannier self-duality of critical quantum chains is examined from the perspective of model wave functions. We demonstrate, using the transverse-field Ising chain and the 3-state Potts chain as examples, that the symmetry operator for the Kramers-Wannier self-duality follows in a simple and direct way from a ‘generalised’ translation symmetry of the model wave function in the anyonic fusion basis. This translation operation, in turn, comprises a sequence of F-moves in the underlying fusion category. The symmetry operator thus obtained naturally admits the form of a matrix product operator and obeys non-invertible fusion rules. The findings reveal an intriguing connection between the (non-invertible) translation symmetry on the lattice and topological aspects of the conformal field theory describing the scaling limit.},
keywords = {CSIC-4.7},
pubstate = {published},
tppubtype = {article}
}
The Kramers-Wannier self-duality of critical quantum chains is examined from the perspective of model wave functions. We demonstrate, using the transverse-field Ising chain and the 3-state Potts chain as examples, that the symmetry operator for the Kramers-Wannier self-duality follows in a simple and direct way from a ‘generalised’ translation symmetry of the model wave function in the anyonic fusion basis. This translation operation, in turn, comprises a sequence of F-moves in the underlying fusion category. The symmetry operator thus obtained naturally admits the form of a matrix product operator and obeys non-invertible fusion rules. The findings reveal an intriguing connection between the (non-invertible) translation symmetry on the lattice and topological aspects of the conformal field theory describing the scaling limit.
Garcia-de-Andoin, M.; Álvarez-Ahedo, A.; Franco-Rubio, A.; Sanz, M.
Impact and mitigation of Hamiltonian characterization errors in digital-analog quantum computation Working paper
2025.
Resumen | Enlaces | BibTeX | Etiquetas: UPV/EHU
@workingpaper{nokey,
title = {Impact and mitigation of Hamiltonian characterization errors in digital-analog quantum computation},
author = {Garcia-de-Andoin, M. and Álvarez-Ahedo, A. and Franco-Rubio, A. and Sanz, M. },
url = {https://arxiv.org/abs/2505.03642},
doi = {doi.org/10.48550/arXiv.2505.03642},
year = {2025},
date = {2025-05-06},
urldate = {2025-05-06},
abstract = {Digital-analog is a universal quantum computing paradigm which employs the natural entangling
Hamiltonian of the system and single-qubit gates as resources. Here, we study the stability of
these protocols against Hamiltonian characterization errors. For this, we bound the maximum
separation between the target and the implemented Hamiltonians. Additionally, we obtain an upper
bound for the deviation in the expected value of an observable. We further propose a protocol for
mitigating calibration errors which resembles dynamical-decoupling techniques. These results open
the possibility of scaling digital-analog to intermediate and large scale systems while having an
estimation on the errors committed.},
keywords = {UPV/EHU},
pubstate = {published},
tppubtype = {workingpaper}
}
Digital-analog is a universal quantum computing paradigm which employs the natural entangling
Hamiltonian of the system and single-qubit gates as resources. Here, we study the stability of
these protocols against Hamiltonian characterization errors. For this, we bound the maximum
separation between the target and the implemented Hamiltonians. Additionally, we obtain an upper
bound for the deviation in the expected value of an observable. We further propose a protocol for
mitigating calibration errors which resembles dynamical-decoupling techniques. These results open
the possibility of scaling digital-analog to intermediate and large scale systems while having an
estimation on the errors committed.
Hamiltonian of the system and single-qubit gates as resources. Here, we study the stability of
these protocols against Hamiltonian characterization errors. For this, we bound the maximum
separation between the target and the implemented Hamiltonians. Additionally, we obtain an upper
bound for the deviation in the expected value of an observable. We further propose a protocol for
mitigating calibration errors which resembles dynamical-decoupling techniques. These results open
the possibility of scaling digital-analog to intermediate and large scale systems while having an
estimation on the errors committed.
Tejedor, M.; Casas, B.; Conejero, J.; Cervera-Lierta, A.; R Badia, M.
Distributed Quantum Circuit Cutting for Hybrid Quantum-Classical High-Performance Computing Working paper
2025.
Resumen | Enlaces | BibTeX | Etiquetas: BSC
@workingpaper{nokey,
title = {Distributed Quantum Circuit Cutting for Hybrid Quantum-Classical High-Performance Computing},
author = {Tejedor, M. and Casas, B. and Conejero, J. and Cervera-Lierta, A. and Badia, R,M. },
url = {https://arxiv.org/pdf/2505.01184},
doi = {doi.org/10.48550/arXiv.2505.01184},
year = {2025},
date = {2025-05-05},
urldate = {2025-05-05},
abstract = {Most quantum computers today are constrained by hardware limitations, particularly the number of available qubits, causing significant challenges for executing large-scale quantum algorithms. Circuit cutting has emerged as a key technique to overcome these limitations by decomposing large quantum circuits into smaller subcircuits that can be executed independently and later reconstructed. In this work, we introduce Qdislib, a distributed and flexible library for quantum circuit cutting, designed to seamlessly integrate with hybrid quantum-classical high-performance computing (HPC) systems. Qdislib employs a graph-based representation of quantum circuits to enable efficient partitioning, manipulation and execution, supporting both wire cutting and gate cutting techniques. The library is compatible with multiple quantum computing libraries, including Qiskit and Qibo, and leverages distributed computing frameworks to execute subcircuits across CPUs, GPUs, and quantum processing units (QPUs) in a fully parallelized manner. We present a proof of concept demonstrating how Qdislib enables the distributed execution of quantum circuits across heterogeneous computing resources, showcasing its potential for scalable quantum-classical workflows.},
keywords = {BSC},
pubstate = {published},
tppubtype = {workingpaper}
}
Most quantum computers today are constrained by hardware limitations, particularly the number of available qubits, causing significant challenges for executing large-scale quantum algorithms. Circuit cutting has emerged as a key technique to overcome these limitations by decomposing large quantum circuits into smaller subcircuits that can be executed independently and later reconstructed. In this work, we introduce Qdislib, a distributed and flexible library for quantum circuit cutting, designed to seamlessly integrate with hybrid quantum-classical high-performance computing (HPC) systems. Qdislib employs a graph-based representation of quantum circuits to enable efficient partitioning, manipulation and execution, supporting both wire cutting and gate cutting techniques. The library is compatible with multiple quantum computing libraries, including Qiskit and Qibo, and leverages distributed computing frameworks to execute subcircuits across CPUs, GPUs, and quantum processing units (QPUs) in a fully parallelized manner. We present a proof of concept demonstrating how Qdislib enables the distributed execution of quantum circuits across heterogeneous computing resources, showcasing its potential for scalable quantum-classical workflows.
S. Ding Romero, Y.; Chen, Xi.; Ban, Y.
Scrambling in the charging of quantum batteries Artículo de revista
En: High Energy Physics, vol. 2025, no 21, 2025.
Resumen | Enlaces | BibTeX | Etiquetas: UPV/EHU
@article{nokey,
title = {Scrambling in the charging of quantum batteries},
author = {Romero, S. Ding, Y. and Chen, Xi. and Ban, Y.},
url = {https://link.springer.com/content/pdf/10.1007/JHEP05(2025)021.pdf},
doi = {doi.org/10.1007/JHEP05(2025)021},
year = {2025},
date = {2025-05-05},
journal = {High Energy Physics},
volume = {2025},
number = {21},
abstract = {Exponentially fast scrambling of an initial state characterizes quantum chaotic systems. Given the importance of quickly populating higher energy levels from low-energy states in quantum battery charging protocols, this work investigates the role of quantum scrambling in quantum batteries and its effect on optimal power and charging times by means of the Sachdev-Ye-Kitaev model, a maximally-chaotic black hole physics model that has been recently proposed as a quantum battery. We adopt a bare representation with normalized bandwidths to suppress system energy dependence. To our knowledge, this is the first in-depth exploration of quantum scrambling in the context of quantum batteries. By analyzing the dynamics of out-of-time-order correlators, our findings indicate that quantum scrambling does not necessarily lead to faster charging, despite its potential for accelerating the process.},
keywords = {UPV/EHU},
pubstate = {published},
tppubtype = {article}
}
Exponentially fast scrambling of an initial state characterizes quantum chaotic systems. Given the importance of quickly populating higher energy levels from low-energy states in quantum battery charging protocols, this work investigates the role of quantum scrambling in quantum batteries and its effect on optimal power and charging times by means of the Sachdev-Ye-Kitaev model, a maximally-chaotic black hole physics model that has been recently proposed as a quantum battery. We adopt a bare representation with normalized bandwidths to suppress system energy dependence. To our knowledge, this is the first in-depth exploration of quantum scrambling in the context of quantum batteries. By analyzing the dynamics of out-of-time-order correlators, our findings indicate that quantum scrambling does not necessarily lead to faster charging, despite its potential for accelerating the process.
Rout, S.; Sakharwade, N.; Sankar Bhattacharya, S.; Ramanathan, R.; Horodecki, P.
Unbounded quantum advantage in communication with minimal input scaling Artículo de revista
En: Physical Review Research, 2025.
Resumen | Enlaces | BibTeX | Etiquetas: UAB
@article{nokey,
title = {Unbounded quantum advantage in communication with minimal input scaling},
author = {Rout, S. and Sakharwade, N. and Sankar Bhattacharya, S. and Ramanathan, R. and Horodecki, P. },
url = {https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.7.023104},
doi = {doi.org/10.1103/PhysRevResearch.7.023104},
year = {2025},
date = {2025-04-30},
journal = {Physical Review Research},
abstract = {In communication complexity-like problems, previous studies have shown either an exponential quantum advantage or an unbounded quantum advantage with an exponentially large input set Θ(2𝑛) bit with respect to classical communication Θ(𝑛) bit. In the former, the quantum and classical separation grows exponentially in input while the latter's quantum communication resource is a constant. Remarkably, it was still open whether an unbounded quantum advantage exists while the inputs do not scale exponentially. Here we answer this question affirmatively using an input size of optimal order. Considering two variants as tasks: (1) distributed computation of relation and (2) relation reconstruction, we study the one-way zero-error communication complexity of a relation induced by a distributed clique labeling problem for orthogonality graphs. While we prove no quantum advantage in the first task, we show an unbounded quantum advantage in relation reconstruction without public coins. Specifically, for a class of graphs with order 𝑚, the quantum complexity is Θ(1) while the classical complexity is Θ(log2𝑚). Remarkably, the input size is Θ(log2𝑚) bit and the order of its scaling with respect to classical communication is minimal. This is exponentially better compared to previous works. Additionally, we prove a lower bound (linear in the number of maximum cliques) on the amount of classical public coin necessary to overcome the separation in the scenario of restricted communication and connect this to the existence of orthogonal arrays. Finally, we highlight some applications of this task to semi-device-independent dimension witnessing as well as to the detection of mutually unbiased bases.},
keywords = {UAB},
pubstate = {published},
tppubtype = {article}
}
In communication complexity-like problems, previous studies have shown either an exponential quantum advantage or an unbounded quantum advantage with an exponentially large input set Θ(2𝑛) bit with respect to classical communication Θ(𝑛) bit. In the former, the quantum and classical separation grows exponentially in input while the latter's quantum communication resource is a constant. Remarkably, it was still open whether an unbounded quantum advantage exists while the inputs do not scale exponentially. Here we answer this question affirmatively using an input size of optimal order. Considering two variants as tasks: (1) distributed computation of relation and (2) relation reconstruction, we study the one-way zero-error communication complexity of a relation induced by a distributed clique labeling problem for orthogonality graphs. While we prove no quantum advantage in the first task, we show an unbounded quantum advantage in relation reconstruction without public coins. Specifically, for a class of graphs with order 𝑚, the quantum complexity is Θ(1) while the classical complexity is Θ(log2𝑚). Remarkably, the input size is Θ(log2𝑚) bit and the order of its scaling with respect to classical communication is minimal. This is exponentially better compared to previous works. Additionally, we prove a lower bound (linear in the number of maximum cliques) on the amount of classical public coin necessary to overcome the separation in the scenario of restricted communication and connect this to the existence of orthogonal arrays. Finally, we highlight some applications of this task to semi-device-independent dimension witnessing as well as to the detection of mutually unbiased bases.
Navarro, J.; Ravell Rodríguez, R.; Sanz, M.
Existence of unbiased estimators in discrete quantum systems Artículo de revista
En: Physical Review Research, vol. 7, 2025.
Resumen | Enlaces | BibTeX | Etiquetas: UPV/EHU
@article{nokey,
title = {Existence of unbiased estimators in discrete quantum systems},
author = {Navarro, J. and Ravell Rodríguez, R. and Sanz, M. },
url = {https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.7.023060},
doi = {doi.org/10.1103/PhysRevResearch.7.023060},
year = {2025},
date = {2025-04-16},
journal = {Physical Review Research},
volume = {7},
abstract = {The Cramér-Rao bound serves as a crucial lower limit for the mean square error of an estimator in frequentist parameter estimation. Paradoxically, it requires highly accurate prior knowledge of the estimated parameter for constructing the optimal unbiased estimator. In contrast, Bhattacharyya bounds offer a more robust estimation framework with respect to prior accuracy by introducing additional constraints on the estimator. In this work, we examine divergences that arise in the computation of these bounds and establish the conditions under which they remain valid. Notably, we show that when the number of constraints exceeds the number of measurement outcomes, an estimator with finite variance typically does not exist. Furthermore, we systematically investigate the properties of these bounds using paradigmatic examples, comparing them to the Cramér-Rao and Bayesian approaches.},
keywords = {UPV/EHU},
pubstate = {published},
tppubtype = {article}
}
The Cramér-Rao bound serves as a crucial lower limit for the mean square error of an estimator in frequentist parameter estimation. Paradoxically, it requires highly accurate prior knowledge of the estimated parameter for constructing the optimal unbiased estimator. In contrast, Bhattacharyya bounds offer a more robust estimation framework with respect to prior accuracy by introducing additional constraints on the estimator. In this work, we examine divergences that arise in the computation of these bounds and establish the conditions under which they remain valid. Notably, we show that when the number of constraints exceeds the number of measurement outcomes, an estimator with finite variance typically does not exist. Furthermore, we systematically investigate the properties of these bounds using paradigmatic examples, comparing them to the Cramér-Rao and Bayesian approaches.
Sannia, A.; Giorgi, G. L.; Longhi, S.; Zambrini, R.
Liouvillian skin effect in quantum neural networks Artículo de revista
En: Optica Quantum , vol. 3, iss. 2, pp. 189–194 , 2025.
Resumen | Enlaces | BibTeX | Etiquetas: UIB
@article{nokey,
title = {Liouvillian skin effect in quantum neural networks},
author = {Sannia, A. and Giorgi, G. L. and Longhi, S. and Zambrini, R. },
url = {https://opg.optica.org/opticaq/fulltext.cfm?uri=opticaq-3-2-189&id=569978},
doi = {doi.org/10.1364/OPTICAQ.541744},
year = {2025},
date = {2025-04-04},
urldate = {2025-04-04},
journal = {Optica Quantum },
volume = {3},
issue = {2},
pages = {189–194 },
abstract = {In the field of dissipative systems, the non-Hermitian skin effect has generated significant interest due to its unexpected implications. A system is said to exhibit a skin effect if its properties are largely affected by the boundary conditions. Despite the burgeoning interest, the potential impact of this phenomenon on emerging quantum technologies remains unexplored. In this work, we address this gap by demonstrating that quantum neural networks can exhibit this behavior and that skin effects, beyond their fundamental interest, can also be exploited in computational tasks. Specifically, we show that the performance of a given complex network used as a quantum reservoir computer is dictated solely by the boundary conditions of a dissipative line within its architecture. The closure of one (edge) link is found to drastically change the performance in time-series processing, proving the possibility of exploiting skin effects for machine learning.},
keywords = {UIB},
pubstate = {published},
tppubtype = {article}
}
In the field of dissipative systems, the non-Hermitian skin effect has generated significant interest due to its unexpected implications. A system is said to exhibit a skin effect if its properties are largely affected by the boundary conditions. Despite the burgeoning interest, the potential impact of this phenomenon on emerging quantum technologies remains unexplored. In this work, we address this gap by demonstrating that quantum neural networks can exhibit this behavior and that skin effects, beyond their fundamental interest, can also be exploited in computational tasks. Specifically, we show that the performance of a given complex network used as a quantum reservoir computer is dictated solely by the boundary conditions of a dissipative line within its architecture. The closure of one (edge) link is found to drastically change the performance in time-series processing, proving the possibility of exploiting skin effects for machine learning.
Gonzalez-Raya, T.; Mena, A.; Lazo, M.; L., Leggio; Novoa, D.; Sanz, M.
Entanglement transfer during quantum frequency conversion in gas-filled hollow-core fibers Artículo de revista
En: APL Photonics, vol. 10, 2025.
Resumen | Enlaces | BibTeX | Etiquetas: UPV/EHU
@article{nokey,
title = {Entanglement transfer during quantum frequency conversion in gas-filled hollow-core fibers},
author = {Gonzalez-Raya, T. and Mena, A. and Lazo, M. and Leggio L. and Novoa, D. and Sanz, M. },
url = {https://pubs.aip.org/aip/app/article/10/4/041302/3341958/Entanglement-transfer-during-quantum-frequency},
doi = {doi.org/10.1063/5.0246782},
year = {2025},
date = {2025-04-02},
journal = {APL Photonics},
volume = {10},
abstract = {Quantum transduction is essential for the future hybrid quantum networks, connecting devices across different spectral ranges. In this regard, molecular modulation in hollow-core fibers has proven to be exceptional for efficient and tunable frequency conversion of arbitrary light fields down to the single-photon limit. However, insights into this conversion method for quantum light have remained elusive beyond standard semi-classical models. In this Letter, we employ a quantum Hamiltonian framework to characterize the behavior of entanglement during molecular modulation while describing the quantum dynamics of both molecules and photons in agreement with recent experiments. In particular, apart from obtaining analytical expressions for the final opto-molecular states, our model predicts a close correlation between the evolution of the average photon numbers and the transfer of entanglement between the interacting parties. These results will contribute to the development of new fiber-based strategies to tackle the challenges associated with the upcoming generation of lightwave quantum technologies.},
keywords = {UPV/EHU},
pubstate = {published},
tppubtype = {article}
}
Quantum transduction is essential for the future hybrid quantum networks, connecting devices across different spectral ranges. In this regard, molecular modulation in hollow-core fibers has proven to be exceptional for efficient and tunable frequency conversion of arbitrary light fields down to the single-photon limit. However, insights into this conversion method for quantum light have remained elusive beyond standard semi-classical models. In this Letter, we employ a quantum Hamiltonian framework to characterize the behavior of entanglement during molecular modulation while describing the quantum dynamics of both molecules and photons in agreement with recent experiments. In particular, apart from obtaining analytical expressions for the final opto-molecular states, our model predicts a close correlation between the evolution of the average photon numbers and the transfer of entanglement between the interacting parties. These results will contribute to the development of new fiber-based strategies to tackle the challenges associated with the upcoming generation of lightwave quantum technologies.
Biswas, S.; Rico, E.; Grass, T.
Ring-exchange physics in a chain of three-level ions Artículo de revista
En: Quantum , 2025.
Resumen | Enlaces | BibTeX | Etiquetas: UPV/EHU
@article{nokey,
title = {Ring-exchange physics in a chain of three-level ions},
author = {Biswas, S. and Rico, E. and Grass, T. },
url = {https://quantum-journal.org/papers/q-2025-04-01-1683/},
doi = {doi.org/10.22331/q-2025-04-01-1683},
year = {2025},
date = {2025-04-01},
journal = {Quantum },
abstract = {In the presence of ring exchange interactions, bosons in a ladder-like lattice may form the bosonic analogon of a correlated metal, known as the d-wave Bose liquid (DBL). In this paper, we show that a chain of trapped ions with three internal levels can mimic a ladder-like system constrained to a maximum occupation of one boson per rung. The setup enables tunable ring exchange interactions, transitioning between a polarized regime with all bosons confined to one leg and the DBL regime. The latter state is characterized by a splitting of the peak in the momentum distribution and an oscillating pair correlation function.},
keywords = {UPV/EHU},
pubstate = {published},
tppubtype = {article}
}
In the presence of ring exchange interactions, bosons in a ladder-like lattice may form the bosonic analogon of a correlated metal, known as the d-wave Bose liquid (DBL). In this paper, we show that a chain of trapped ions with three internal levels can mimic a ladder-like system constrained to a maximum occupation of one boson per rung. The setup enables tunable ring exchange interactions, transitioning between a polarized regime with all bosons confined to one leg and the DBL regime. The latter state is characterized by a splitting of the peak in the momentum distribution and an oscillating pair correlation function.
Schindler, J.; Strasberg, P.; Galke, N.; Winter, A.; Jabbour, M.
Unification of observational entropy with maximum entropy principles Working paper
2025.
Resumen | Enlaces | BibTeX | Etiquetas: UAB
@workingpaper{nokey,
title = {Unification of observational entropy with maximum entropy principles},
author = {Schindler, J. and Strasberg, P. and Galke, N. and Winter, A. and Jabbour, M.
},
url = {https://arxiv.org/abs/2503.15612},
doi = {doi.org/10.48550/arXiv.2503.15612},
year = {2025},
date = {2025-03-19},
abstract = {We introduce a definition of coarse-grained entropy that unifies measurement-based (observational entropy) and max-entropy-based (Jaynes) approaches to coarse-graining, by identifying physical constraints with information theoretic priors. The definition is shown to include as special cases most other entropies of interest in physics. We then consider second laws, showing that the definition admits new entropy increase theorems and connections to thermodynamics. We survey mathematical properties of the definition, and show it resolves some pathologies of the traditional observational entropy in infinite dimensions. Finally, we study the dynamics of this entropy in a quantum random matrix model and a classical hard sphere gas. Together the results suggest that this generalized observational entropy can form the basis of a highly general approach to statistical mechanics.},
keywords = {UAB},
pubstate = {published},
tppubtype = {workingpaper}
}
We introduce a definition of coarse-grained entropy that unifies measurement-based (observational entropy) and max-entropy-based (Jaynes) approaches to coarse-graining, by identifying physical constraints with information theoretic priors. The definition is shown to include as special cases most other entropies of interest in physics. We then consider second laws, showing that the definition admits new entropy increase theorems and connections to thermodynamics. We survey mathematical properties of the definition, and show it resolves some pathologies of the traditional observational entropy in infinite dimensions. Finally, we study the dynamics of this entropy in a quantum random matrix model and a classical hard sphere gas. Together the results suggest that this generalized observational entropy can form the basis of a highly general approach to statistical mechanics.
Rodriguez-Grasa, P.; Ibarrondo, R.; Gonzalez-Conde, J.; Ban, Y.; Rebentrost, P.; Sanz, M.
Quantum approximated cloning-assisted density matrix exponentiation Artículo de revista
En: Physical Review Research, vol. 7, 2025.
Resumen | Enlaces | BibTeX | Etiquetas: UPV/EHU
@article{nokey,
title = {Quantum approximated cloning-assisted density matrix exponentiation},
author = {Rodriguez-Grasa, P. and Ibarrondo, R. and Gonzalez-Conde, J. and Ban, Y. and Rebentrost, P. and Sanz, M. },
url = {https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.7.013264},
doi = {doi.org/10.1103/PhysRevResearch.7.013264},
year = {2025},
date = {2025-03-12},
journal = {Physical Review Research},
volume = {7},
abstract = {Classical information loading is an essential task for many processing quantum algorithms, constituting a cornerstone in the field of quantum machine learning. In particular, the embedding techniques based on Hamiltonian simulation techniques enable the loading of matrices into quantum computers. A representative example of these methods is the Lloyd-Mohseni-Rebentrost (LMR) protocol, which efficiently implements matrix exponentiation when multiple copies of a quantum state are available. However, this is a quite ideal setup, and in a realistic scenario, the copies are limited and the noncloning theorem prevents one from producing more exact copies in order to increase the accuracy of the protocol. Here, we propose a method to circumvent this limitation by introducing imperfect quantum copies, which significantly improve the performance of the LMR when the eigenvectors are known.},
keywords = {UPV/EHU},
pubstate = {published},
tppubtype = {article}
}
Classical information loading is an essential task for many processing quantum algorithms, constituting a cornerstone in the field of quantum machine learning. In particular, the embedding techniques based on Hamiltonian simulation techniques enable the loading of matrices into quantum computers. A representative example of these methods is the Lloyd-Mohseni-Rebentrost (LMR) protocol, which efficiently implements matrix exponentiation when multiple copies of a quantum state are available. However, this is a quite ideal setup, and in a realistic scenario, the copies are limited and the noncloning theorem prevents one from producing more exact copies in order to increase the accuracy of the protocol. Here, we propose a method to circumvent this limitation by introducing imperfect quantum copies, which significantly improve the performance of the LMR when the eigenvectors are known.
Fanizza, M.; Galke, N.; Lumbreras, J.; Rouzé, C.; Winter, A.
Learning finitely-correlated states: stability of the spectral reconstruction Working paper
2025.
Resumen | Enlaces | BibTeX | Etiquetas: UAB
@workingpaper{nokey,
title = {Learning finitely-correlated states: stability of the spectral reconstruction},
author = {Fanizza, M. and Galke, N. and Lumbreras, J. and Rouzé, C. and Winter, A. },
url = {https://arxiv.org/abs/2312.07516},
doi = {doi.org/10.48550/arXiv.2312.07516},
year = {2025},
date = {2025-03-06},
abstract = {Matrix product operators allow efficient descriptions (or realizations) of states on a 1D lattice. We consider the task of learning a realization of minimal dimension from copies of an unknown state, such that the resulting operator is close to the density matrix in trace norm. For finitely correlated translation-invariant states on an infinite chain, a realization of minimal dimension can be exactly reconstructed via linear algebra operations from the marginals of a size depending on the representation dimension. We establish a bound on the trace norm error for an algorithm that estimates a candidate realization from estimates of these marginals and outputs a matrix product operator, estimating the state of a chain of arbitrary length . This bound allows us to establish an upper bound on the sample complexity of the learning task, with an explicit dependence on the site dimension, realization dimension and spectral properties of a certain map constructed from the state. A refined error bound can be proven for -finitely correlated states, which have an operational interpretation in terms of sequential quantum channels applied to the memory system. We can also obtain an analogous error bound for a class of matrix product density operators on a finite chain reconstructible by local marginals. In this case, a linear number of marginals must be estimated, obtaining a sample complexity of . The learning algorithm also works for states that are sufficiently close to a finitely correlated state, with the potential of providing competitive algorithms for other interesting families of states.},
keywords = {UAB},
pubstate = {published},
tppubtype = {workingpaper}
}
Matrix product operators allow efficient descriptions (or realizations) of states on a 1D lattice. We consider the task of learning a realization of minimal dimension from copies of an unknown state, such that the resulting operator is close to the density matrix in trace norm. For finitely correlated translation-invariant states on an infinite chain, a realization of minimal dimension can be exactly reconstructed via linear algebra operations from the marginals of a size depending on the representation dimension. We establish a bound on the trace norm error for an algorithm that estimates a candidate realization from estimates of these marginals and outputs a matrix product operator, estimating the state of a chain of arbitrary length . This bound allows us to establish an upper bound on the sample complexity of the learning task, with an explicit dependence on the site dimension, realization dimension and spectral properties of a certain map constructed from the state. A refined error bound can be proven for -finitely correlated states, which have an operational interpretation in terms of sequential quantum channels applied to the memory system. We can also obtain an analogous error bound for a class of matrix product density operators on a finite chain reconstructible by local marginals. In this case, a linear number of marginals must be estimated, obtaining a sample complexity of . The learning algorithm also works for states that are sufficiently close to a finitely correlated state, with the potential of providing competitive algorithms for other interesting families of states.
Llorens, S.; González, W.; Sentís, G.; Calsamiglia, J.; Muñoz-Tapia, R.; Bagan, Em.
Quantum Edge Detection Artículo de revista
En: Quantum, vol. 8, pp. 1289, 2025.
Resumen | Enlaces | BibTeX | Etiquetas: UAB
@article{nokey,
title = {Quantum Edge Detection},
author = {Llorens, S. and González, W. and Sentís, G. and Calsamiglia, J. and Muñoz-Tapia, R. and Bagan, Em.},
url = {https://quantum-journal.org/papers/q-2025-04-03-1687/},
doi = {doi.org/10.22331/q-2025-04-03-1687},
year = {2025},
date = {2025-03-04},
journal = {Quantum},
volume = {8},
pages = {1289},
abstract = {We consider a quantum system that is being continuously monitored, giving rise to a measurement signal. From such a stream of data, information needs to be inferred about the underlying system's dynamics. Here we focus on hypothesis testing problems and put forward the usage of sequential strategies where the signal is analyzed in real time, allowing the experiment to be concluded as soon as the underlying hypothesis can be identified with a certified prescribed success probability. We analyze the performance of sequential tests by studying the stopping-time behavior, showing a considerable advantage over currently-used strategies based on a fixed predetermined measurement time.},
keywords = {UAB},
pubstate = {published},
tppubtype = {article}
}
We consider a quantum system that is being continuously monitored, giving rise to a measurement signal. From such a stream of data, information needs to be inferred about the underlying system's dynamics. Here we focus on hypothesis testing problems and put forward the usage of sequential strategies where the signal is analyzed in real time, allowing the experiment to be concluded as soon as the underlying hypothesis can be identified with a certified prescribed success probability. We analyze the performance of sequential tests by studying the stopping-time behavior, showing a considerable advantage over currently-used strategies based on a fixed predetermined measurement time.
Dastbasteh, R.; Sanz Larrarte, O.; J. deMarti iOlius Etxezarreta Martinez, A.; Oliva del Moral, J.; Crespo Bofill, P.
Quantum CSS Duadic and Triadic Codes: New Insights and Properties Artículo de revista
En: Lecture Notes in Computer Science, vol. 15 176, 2025.
Resumen | Enlaces | BibTeX | Etiquetas: TECNUN
@article{nokey,
title = {Quantum CSS Duadic and Triadic Codes: New Insights and Properties},
author = {Dastbasteh, R. and Sanz Larrarte, O. and Etxezarreta Martinez, J. deMarti iOlius, A. and Oliva del Moral, J. and Crespo Bofill, P. },
url = {https://link.springer.com/chapter/10.1007/978-3-031-81824-0_5},
doi = { https://doi.org/10.48550/arXiv.2407.07753},
year = {2025},
date = {2025-02-28},
urldate = {2025-02-28},
journal = {Lecture Notes in Computer Science},
volume = {15 176},
abstract = {In this study, we investigate the construction of quantum CSS duadic codes with dimensions greater than one. We introduce a method for extending smaller splittings of quantum duadic codes to create larger, potentially degenerate quantum duadic codes. Furthermore, we present a technique for computing or bounding the minimum distances of quantum codes constructed through this approach. Additionally, we introduce quantum CSS triadic codes, a family of quantum codes with a rate of at least 1/3.},
keywords = {TECNUN},
pubstate = {published},
tppubtype = {article}
}
In this study, we investigate the construction of quantum CSS duadic codes with dimensions greater than one. We introduce a method for extending smaller splittings of quantum duadic codes to create larger, potentially degenerate quantum duadic codes. Furthermore, we present a technique for computing or bounding the minimum distances of quantum codes constructed through this approach. Additionally, we introduce quantum CSS triadic codes, a family of quantum codes with a rate of at least 1/3.
Styliaris, G.; Trivedi, R.; Pérez-García, D.; Cirac, J. I.
Matrix-product unitaries: Beyond quantum cellular automata Artículo de revista
En: 2025.
Resumen | Enlaces | BibTeX | Etiquetas: UCM-4.2
@article{nokey,
title = {Matrix-product unitaries: Beyond quantum cellular automata},
author = {Styliaris, G. and Trivedi, R. and Pérez-García, D. and Cirac, J. I.
},
url = {https://quantum-journal.org/papers/q-2025-02-25-1645/},
doi = {doi.org/10.22331/q-2025-02-25-1645},
year = {2025},
date = {2025-02-25},
urldate = {2025-02-20},
abstract = {Matrix-product unitaries (MPU) are 1D tensor networks describing time evolution and unitary symmetries of quantum systems, while their action on states by construction preserves the entanglement area law. MPU which are formed by a single repeated tensor are known to coincide with 1D quantum cellular automata (QCA), i.e., unitaries with an exact light cone. However, this correspondence breaks down for MPU with open boundary conditions, even if the resulting operator is translation-invariant. Such unitaries can turn short- to long-range correlations and thus alter the underlying phase of matter. Here we make the first steps towards a theory of MPU with uniform bulk but arbitrary boundary. In particular, we study the structure of a subclass with a direct-sum form which maximally violates the QCA property. We also consider the general case of MPU formed by site-dependent (nonuniform) tensors and show a correspondence between MPU and locally maximally entanglable states.},
keywords = {UCM-4.2},
pubstate = {published},
tppubtype = {article}
}
Matrix-product unitaries (MPU) are 1D tensor networks describing time evolution and unitary symmetries of quantum systems, while their action on states by construction preserves the entanglement area law. MPU which are formed by a single repeated tensor are known to coincide with 1D quantum cellular automata (QCA), i.e., unitaries with an exact light cone. However, this correspondence breaks down for MPU with open boundary conditions, even if the resulting operator is translation-invariant. Such unitaries can turn short- to long-range correlations and thus alter the underlying phase of matter. Here we make the first steps towards a theory of MPU with uniform bulk but arbitrary boundary. In particular, we study the structure of a subclass with a direct-sum form which maximally violates the QCA property. We also consider the general case of MPU formed by site-dependent (nonuniform) tensors and show a correspondence between MPU and locally maximally entanglable states.
Rodriguez-Grasa, P.; Farzan-Rodríguez, R.; Novelli, G.; Ban, Y.; Sanz, M.
Satellite image classification with neural quantum kernels Artículo de revista
En: Machine Learning: Science and Technology, vol. 6, no 1, 2025.
Resumen | Enlaces | BibTeX | Etiquetas: UPV/EHU
@article{nokey,
title = {Satellite image classification with neural quantum kernels},
author = {Rodriguez-Grasa, P. and Farzan-Rodríguez, R. and Novelli, G. and Ban, Y. and Sanz, M. },
url = {https://iopscience.iop.org/article/10.1088/2632-2153/ada86c/pdf},
doi = {10.1088/2632-2153/ada86c},
year = {2025},
date = {2025-02-18},
journal = {Machine Learning: Science and Technology},
volume = {6},
number = {1},
abstract = {Achieving practical applications of quantum machine learning (QML) for real-world scenarios
remains challenging despite significant theoretical progress. This paper proposes a novel approach
for classifying satellite images, a task of particular relevance to the earth observation industry, using
QML techniques. Specifically, we focus on classifying images that contain solar panels, addressing a
complex real-world classification problem. Our approach begins with classical pre-processing to
reduce the dimensionality of the satellite image dataset. We then apply neural quantum
kernels-quantum kernels derived from trained quantum neural networks-for classification. We
evaluate several strategies within this framework, demonstrating results that are competitive with
the best classical methods. Key findings include the robustness of or results and their scalability,
with successful performance achieved up to 8 qubits.
},
keywords = {UPV/EHU},
pubstate = {published},
tppubtype = {article}
}
Achieving practical applications of quantum machine learning (QML) for real-world scenarios
remains challenging despite significant theoretical progress. This paper proposes a novel approach
for classifying satellite images, a task of particular relevance to the earth observation industry, using
QML techniques. Specifically, we focus on classifying images that contain solar panels, addressing a
complex real-world classification problem. Our approach begins with classical pre-processing to
reduce the dimensionality of the satellite image dataset. We then apply neural quantum
kernels-quantum kernels derived from trained quantum neural networks-for classification. We
evaluate several strategies within this framework, demonstrating results that are competitive with
the best classical methods. Key findings include the robustness of or results and their scalability,
with successful performance achieved up to 8 qubits.
remains challenging despite significant theoretical progress. This paper proposes a novel approach
for classifying satellite images, a task of particular relevance to the earth observation industry, using
QML techniques. Specifically, we focus on classifying images that contain solar panels, addressing a
complex real-world classification problem. Our approach begins with classical pre-processing to
reduce the dimensionality of the satellite image dataset. We then apply neural quantum
kernels-quantum kernels derived from trained quantum neural networks-for classification. We
evaluate several strategies within this framework, demonstrating results that are competitive with
the best classical methods. Key findings include the robustness of or results and their scalability,
with successful performance achieved up to 8 qubits.
