Pub Date : 2026-02-05DOI: 10.1088/2058-9565/ae3b70
Dario De Santis, Salvatore Tirone, Stefano Marmi and Vittorio Giovannetti
Quantum computers have strict requirements for the problems that they can efficiently solve. One of the principal limiting factor for the performances of noisy intermediate-scale quantum (NISQ) devices is the number of qubits required by the running algorithm. Several combinatorial optimization problems can be solved with NISQ devices once that a corresponding quadratic unconstrained binary optimization (QUBO) form is derived. Numerous techniques have been proposed to achieve such reformulations and, depending on the method chosen, the number of binary variables required, and therefore of qubits, can vary considerably. The aim of this work is to drastically reduce the variables needed for these QUBO reformulations in order to unlock the possibility to efficiently obtain optimal solutions for a class of optimization problems with NISQ devices. This goal is achieved by introducing novel tools that allow an efficient use of slack variables, even for problems with non-linear constraints, without the need to approximate the starting problem. We divide our new techniques in two independent parts, called the iterative quadratic polynomial and the master-satellite methods. Hence, we show how to apply our techniques in case of an NP-hard optimization problem inspired by a real-world financial scenario called Max-Profit Balance Settlement. We follow by submitting several instances of this problem to two D-wave quantum annealers, comparing the performances of our novel approach with the standard methods used in these scenarios. Moreover, this study allows to appreciate several performance differences between the D-wave Advantage and next-generation Advantage2 quantum annealers. We show that the adoption of our techniques in this context allows to obtain QUBO formulations with significantly fewer slack variables, i.e. around 90% less, and D-wave annealers provide considerably higher correct solution rates, which moreover do not decrease with the input size as fast as when adopting standard techniques.
{"title":"Optimized QUBO formulation methods for quantum computing","authors":"Dario De Santis, Salvatore Tirone, Stefano Marmi and Vittorio Giovannetti","doi":"10.1088/2058-9565/ae3b70","DOIUrl":"https://doi.org/10.1088/2058-9565/ae3b70","url":null,"abstract":"Quantum computers have strict requirements for the problems that they can efficiently solve. One of the principal limiting factor for the performances of noisy intermediate-scale quantum (NISQ) devices is the number of qubits required by the running algorithm. Several combinatorial optimization problems can be solved with NISQ devices once that a corresponding quadratic unconstrained binary optimization (QUBO) form is derived. Numerous techniques have been proposed to achieve such reformulations and, depending on the method chosen, the number of binary variables required, and therefore of qubits, can vary considerably. The aim of this work is to drastically reduce the variables needed for these QUBO reformulations in order to unlock the possibility to efficiently obtain optimal solutions for a class of optimization problems with NISQ devices. This goal is achieved by introducing novel tools that allow an efficient use of slack variables, even for problems with non-linear constraints, without the need to approximate the starting problem. We divide our new techniques in two independent parts, called the iterative quadratic polynomial and the master-satellite methods. Hence, we show how to apply our techniques in case of an NP-hard optimization problem inspired by a real-world financial scenario called Max-Profit Balance Settlement. We follow by submitting several instances of this problem to two D-wave quantum annealers, comparing the performances of our novel approach with the standard methods used in these scenarios. Moreover, this study allows to appreciate several performance differences between the D-wave Advantage and next-generation Advantage2 quantum annealers. We show that the adoption of our techniques in this context allows to obtain QUBO formulations with significantly fewer slack variables, i.e. around 90% less, and D-wave annealers provide considerably higher correct solution rates, which moreover do not decrease with the input size as fast as when adopting standard techniques.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"91 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146115594","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-04DOI: 10.1088/2058-9565/ae3acf
Isabell Jauch, Thomas Strohm, Tino Fuchs and Fedor Jelezko
Quantum optimal control in color center physics plays a crucial role in advancing sensor technology. This study focuses on optimizing microwave pulse shapes within a Ramsey sequence for nitrogen-vacancy centers to enhance sensor sensitivity and signal detection capabilities. We compare state-of-the-art optimization methods, including the dressed chopped randomized basis Nelder–Mead algorithm and covariance matrix adaptation evolutionary strategy, and extend our search to machine learning approaches, such as Gaussian processes and artificial neural networks. These machine learning techniques are specifically designed to provide robust and global solutions that can rapidly adapt to changing environmental conditions. Our results demonstrate more than a sixfold increase in convergence speed compared to conventional methods and considerable contrast improvements with a limited retraining set of 72 samples. Furthermore, we demonstrate that the optimized Ramsey contrast translates into a significant enhancement in the signal-to-noise ratio for detecting synthetic magnetic heart signals. This highlights the potential of machine learning-driven quantum optimal control for developing more flexible, adaptive, and efficient quantum sensing solutions in real-world scenarios.
{"title":"Quantum magnetometry enhanced by machine learning","authors":"Isabell Jauch, Thomas Strohm, Tino Fuchs and Fedor Jelezko","doi":"10.1088/2058-9565/ae3acf","DOIUrl":"https://doi.org/10.1088/2058-9565/ae3acf","url":null,"abstract":"Quantum optimal control in color center physics plays a crucial role in advancing sensor technology. This study focuses on optimizing microwave pulse shapes within a Ramsey sequence for nitrogen-vacancy centers to enhance sensor sensitivity and signal detection capabilities. We compare state-of-the-art optimization methods, including the dressed chopped randomized basis Nelder–Mead algorithm and covariance matrix adaptation evolutionary strategy, and extend our search to machine learning approaches, such as Gaussian processes and artificial neural networks. These machine learning techniques are specifically designed to provide robust and global solutions that can rapidly adapt to changing environmental conditions. Our results demonstrate more than a sixfold increase in convergence speed compared to conventional methods and considerable contrast improvements with a limited retraining set of 72 samples. Furthermore, we demonstrate that the optimized Ramsey contrast translates into a significant enhancement in the signal-to-noise ratio for detecting synthetic magnetic heart signals. This highlights the potential of machine learning-driven quantum optimal control for developing more flexible, adaptive, and efficient quantum sensing solutions in real-world scenarios.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"6 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146116161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-04DOI: 10.1088/2058-9565/ae3b6f
Alena Romanova and Wolfgang Dür
We show how to perform measurement-based quantum computing on qudits (high-dimensional quantum systems) using alternative resource states beyond the cluster state. Estimating overheads for gate decomposition, we find that generalizing standard qubit measurement patterns to the qudit cluster state is suboptimal in most dimensions, so that alternative qudit resource states could enable enhanced computational efficiency. In these resources, the entangling interaction is a block-diagonal Clifford operation rather than the usual controlled-phase gate for cluster states. This simple change has remarkable consequences: the applied entangling operation determines an intrinsic single-qudit gate associated with the resource that drives the quantum computation when performing single-qudit measurements on the resource state. We prove a condition for the intrinsic gate allowing for the measurement-based implementation of arbitrary single-qudit unitaries. Furthermore, we demonstrate for prime-power-dimensional qudits that the complexity of the realization depends linearly both on the dimension and the Pauli order of the intrinsic gate. These insights also allow us to optimize the efficiency of the standard qudit cluster state by effectively mimicking more favorable intrinsic-gate structures, thereby reducing the required measurement depth. Finally, we discuss the required two-dimensional geometry of the resource state for universal measurement-based quantum computing. As concrete examples, we present multiple alternative resource states. In certain dimensions, we show the existence of resource states achieving optimal intrinsic gates, enabling more efficient measurement-based quantum information processing than the qudit cluster state and highlighting the potential of qudit stabilizer state resources for future quantum computing architectures.
{"title":"Measurement-based quantum computing with qudit stabilizer states","authors":"Alena Romanova and Wolfgang Dür","doi":"10.1088/2058-9565/ae3b6f","DOIUrl":"https://doi.org/10.1088/2058-9565/ae3b6f","url":null,"abstract":"We show how to perform measurement-based quantum computing on qudits (high-dimensional quantum systems) using alternative resource states beyond the cluster state. Estimating overheads for gate decomposition, we find that generalizing standard qubit measurement patterns to the qudit cluster state is suboptimal in most dimensions, so that alternative qudit resource states could enable enhanced computational efficiency. In these resources, the entangling interaction is a block-diagonal Clifford operation rather than the usual controlled-phase gate for cluster states. This simple change has remarkable consequences: the applied entangling operation determines an intrinsic single-qudit gate associated with the resource that drives the quantum computation when performing single-qudit measurements on the resource state. We prove a condition for the intrinsic gate allowing for the measurement-based implementation of arbitrary single-qudit unitaries. Furthermore, we demonstrate for prime-power-dimensional qudits that the complexity of the realization depends linearly both on the dimension and the Pauli order of the intrinsic gate. These insights also allow us to optimize the efficiency of the standard qudit cluster state by effectively mimicking more favorable intrinsic-gate structures, thereby reducing the required measurement depth. Finally, we discuss the required two-dimensional geometry of the resource state for universal measurement-based quantum computing. As concrete examples, we present multiple alternative resource states. In certain dimensions, we show the existence of resource states achieving optimal intrinsic gates, enabling more efficient measurement-based quantum information processing than the qudit cluster state and highlighting the potential of qudit stabilizer state resources for future quantum computing architectures.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"30 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146115652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-03DOI: 10.1088/2058-9565/ae3a12
Alejandro D Bendersky, Sergio S Gomez and Rodolfo H Romero
We studied the dynamics of a pair of single-electron double quantum dots (DQDs) under longitudinal and transverse static magnetic fields and time-dependent harmonic modulation of their interaction couplings. We propose to modulate the tunnel coupling between the QDs to produce one-qubit gates and the exchange coupling between DQDs to generate entangling gates, the set of operations required for quantum computing. We developed analytical approximations to set the conditions to control the qubits and applied them to numerical calculations to test the accuracy and robustness of the analytical model. The results shows that the unitary evolution of the two-electron state performs the designed operations even under conditions shifted from the ideal ones.
{"title":"Quantum gates in coupled quantum dots controlled by coupling modulation","authors":"Alejandro D Bendersky, Sergio S Gomez and Rodolfo H Romero","doi":"10.1088/2058-9565/ae3a12","DOIUrl":"https://doi.org/10.1088/2058-9565/ae3a12","url":null,"abstract":"We studied the dynamics of a pair of single-electron double quantum dots (DQDs) under longitudinal and transverse static magnetic fields and time-dependent harmonic modulation of their interaction couplings. We propose to modulate the tunnel coupling between the QDs to produce one-qubit gates and the exchange coupling between DQDs to generate entangling gates, the set of operations required for quantum computing. We developed analytical approximations to set the conditions to control the qubits and applied them to numerical calculations to test the accuracy and robustness of the analytical model. The results shows that the unitary evolution of the two-electron state performs the designed operations even under conditions shifted from the ideal ones.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"184 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146101467","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-02DOI: 10.1088/2058-9565/ae3ace
Özlem Erkılıç, Matthew S Winnel, Aritra Das, Sebastian Kish, Ping Koy Lam, Jie Zhao and Syed M Assad
Quantum communication enables secure information transmission and entanglement distribution, but these tasks are fundamentally limited by the capacities of quantum channels. While quantum repeaters can mitigate losses and noise, entanglement swapping via a central node is ineffective against the Pauli dephasing channel due to degradation from Bell-state measurements. This suggests that purifying distributed Bell states before entanglement swapping is necessary. Although one-way hashing codes are known to saturate the dephasing channel capacity, no explicit two-way purification protocol has previously been shown to achieve this bound. In this work, we present a two-way entanglement purification protocol with an explicit, scalable circuit that asymptotically achieves the dephasing channel capacity. With each iteration, the fidelity of Bell states increases. At the final round, the residual dephasing error is suppressed doubly-exponentially, scaling as , enabling near-perfect Bell pairs for any fixed number of purification rounds n. The explicit circuit we propose is versatile and applicable to any number of Bell pairs, offering a practical solution for mitigating decoherence in quantum networks and distributed quantum computing.
{"title":"Capacity-achieving entanglement purification protocol for Pauli dephasing channel","authors":"Özlem Erkılıç, Matthew S Winnel, Aritra Das, Sebastian Kish, Ping Koy Lam, Jie Zhao and Syed M Assad","doi":"10.1088/2058-9565/ae3ace","DOIUrl":"https://doi.org/10.1088/2058-9565/ae3ace","url":null,"abstract":"Quantum communication enables secure information transmission and entanglement distribution, but these tasks are fundamentally limited by the capacities of quantum channels. While quantum repeaters can mitigate losses and noise, entanglement swapping via a central node is ineffective against the Pauli dephasing channel due to degradation from Bell-state measurements. This suggests that purifying distributed Bell states before entanglement swapping is necessary. Although one-way hashing codes are known to saturate the dephasing channel capacity, no explicit two-way purification protocol has previously been shown to achieve this bound. In this work, we present a two-way entanglement purification protocol with an explicit, scalable circuit that asymptotically achieves the dephasing channel capacity. With each iteration, the fidelity of Bell states increases. At the final round, the residual dephasing error is suppressed doubly-exponentially, scaling as , enabling near-perfect Bell pairs for any fixed number of purification rounds n. The explicit circuit we propose is versatile and applicable to any number of Bell pairs, offering a practical solution for mitigating decoherence in quantum networks and distributed quantum computing.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"140 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146097946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-02DOI: 10.1088/2058-9565/ae3027
Soorya Rethinasamy, Ethan Guo, Alexander Wei, Mark M Wilde and Kristina D Launey
With a view toward addressing the explosive growth in the computational demands of nuclear structure and reactions modeling, we develop a novel quantum algorithm for neutron–nucleus simulations with general potentials, which provides acceptable bound-state energies even in the presence of noise, through the noise-resilient (NR) training method. In particular, the algorithm can now solve for any band-diagonal to full Hamiltonian matrices, as needed to accommodate a general central potential. While we illustrate the approach for exponential Gaussian-like potentials and ab initio inter-cluster potentials (optical potentials), it can also accommodate the complete form of the chiral effective-field-theory nucleon–nucleon potentials used in ab initio nuclear calculations. In this study, we provide a comprehensive analysis for the efficacy of this approach for three different qubit encodings, including the one-hot, binary, and Gray encodings, in terms of the number of Pauli strings and commuting sets involved. We also discuss the advantages of the algorithm for Hamiltonians of various band-diagonal widths, especially critical for potentials of perturbative nature, leading to a drastically reduced runtime of quantum simulations. We prove that the Gray encoding allows for an efficient scaling of the model-space size N (or number of basis states used) and is more resource efficient for band-diagonal Hamiltonians having bandwidth up to N. We introduce a new commutativity scheme called distance-grouped commutativity (DGC) and compare its performance with the well-known qubit-commutativity (QC) scheme. We lay out the explicit grouping of Pauli strings and the diagonalizing unitary under the DGC scheme, and we prove that it outperforms the QC scheme, at the cost of a more complex diagonalizing unitary. Lastly, we provide first solutions of the neutron–alpha dynamics from quantum simulations suitable for noisy intermediate-scale quantum processors, using an optical potential rooted in first principles, as well as a study of the bound-state physics in neutron–Carbon systems, along with a comparison of the efficacy of the one-hot and Gray encodings.
{"title":"Neutron–nucleus dynamics simulations for quantum computers","authors":"Soorya Rethinasamy, Ethan Guo, Alexander Wei, Mark M Wilde and Kristina D Launey","doi":"10.1088/2058-9565/ae3027","DOIUrl":"https://doi.org/10.1088/2058-9565/ae3027","url":null,"abstract":"With a view toward addressing the explosive growth in the computational demands of nuclear structure and reactions modeling, we develop a novel quantum algorithm for neutron–nucleus simulations with general potentials, which provides acceptable bound-state energies even in the presence of noise, through the noise-resilient (NR) training method. In particular, the algorithm can now solve for any band-diagonal to full Hamiltonian matrices, as needed to accommodate a general central potential. While we illustrate the approach for exponential Gaussian-like potentials and ab initio inter-cluster potentials (optical potentials), it can also accommodate the complete form of the chiral effective-field-theory nucleon–nucleon potentials used in ab initio nuclear calculations. In this study, we provide a comprehensive analysis for the efficacy of this approach for three different qubit encodings, including the one-hot, binary, and Gray encodings, in terms of the number of Pauli strings and commuting sets involved. We also discuss the advantages of the algorithm for Hamiltonians of various band-diagonal widths, especially critical for potentials of perturbative nature, leading to a drastically reduced runtime of quantum simulations. We prove that the Gray encoding allows for an efficient scaling of the model-space size N (or number of basis states used) and is more resource efficient for band-diagonal Hamiltonians having bandwidth up to N. We introduce a new commutativity scheme called distance-grouped commutativity (DGC) and compare its performance with the well-known qubit-commutativity (QC) scheme. We lay out the explicit grouping of Pauli strings and the diagonalizing unitary under the DGC scheme, and we prove that it outperforms the QC scheme, at the cost of a more complex diagonalizing unitary. Lastly, we provide first solutions of the neutron–alpha dynamics from quantum simulations suitable for noisy intermediate-scale quantum processors, using an optical potential rooted in first principles, as well as a study of the bound-state physics in neutron–Carbon systems, along with a comparison of the efficacy of the one-hot and Gray encodings.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"8 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146097945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-02DOI: 10.1088/2058-9565/ae397e
Dingjie Lu, Zhao Wang, Jun Liu, Yangfan Li, Wei-Bin Ewe and Zhuangjian Liu
This paper introduces a quantum-enhanced finite element method (FEM) designed for noisy intermediate-scale quantum (NISQ) devices, leveraging variational quantum algorithms (VQAs) to solve engineering partial differential equations. We demonstrate the framework by solving the Euler–Bernoulli beam and the NAFEMS T4 heat transfer problems, which involve Dirichlet, Neumann, and Robin boundary conditions. A key innovation is a ‘set-to-zero’ strategy that incorporates boundary conditions through a correction matrix, , allowing for flexible imposition at any node without domain decomposition. The global stiffness matrix is decomposed into a constant number of Pauli terms, O(1), using the method by Sato et al while boundary terms are handled with a sublinearly scaling partial Pauli measurement technique. The algorithm achieves logarithmic qubit scaling ( qubits for N degrees of freedom(DOF)) and employs shallow, hardware-efficient circuits with empirically trainable depth for small-scale systems. Validation on the Qiskit statevector simulator shows high accuracy. For the Euler–Bernoulli beam problem with 4 to 64 DOF, the algorithm achieves relative errors of 0.5%–1.5% and fidelities of 0.998–0.999. For the NAFEMS T4 heat transfer benchmark, a 5.4% relative error is observed. The VQA converges robustly within 77–350 iterations, though barren plateaus are a known challenge for scaling to larger systems. This work establishes a scalable framework for quantum FEM, offering a significant memory advantage over classical methods and advancing the potential for quantum-enhanced engineering simulations.
{"title":"Quantum finite element algorithm for solving Euler–Bernoulli and heat transfer PDEs with Dirichlet, Neumann, and Robin boundary conditions","authors":"Dingjie Lu, Zhao Wang, Jun Liu, Yangfan Li, Wei-Bin Ewe and Zhuangjian Liu","doi":"10.1088/2058-9565/ae397e","DOIUrl":"https://doi.org/10.1088/2058-9565/ae397e","url":null,"abstract":"This paper introduces a quantum-enhanced finite element method (FEM) designed for noisy intermediate-scale quantum (NISQ) devices, leveraging variational quantum algorithms (VQAs) to solve engineering partial differential equations. We demonstrate the framework by solving the Euler–Bernoulli beam and the NAFEMS T4 heat transfer problems, which involve Dirichlet, Neumann, and Robin boundary conditions. A key innovation is a ‘set-to-zero’ strategy that incorporates boundary conditions through a correction matrix, , allowing for flexible imposition at any node without domain decomposition. The global stiffness matrix is decomposed into a constant number of Pauli terms, O(1), using the method by Sato et al while boundary terms are handled with a sublinearly scaling partial Pauli measurement technique. The algorithm achieves logarithmic qubit scaling ( qubits for N degrees of freedom(DOF)) and employs shallow, hardware-efficient circuits with empirically trainable depth for small-scale systems. Validation on the Qiskit statevector simulator shows high accuracy. For the Euler–Bernoulli beam problem with 4 to 64 DOF, the algorithm achieves relative errors of 0.5%–1.5% and fidelities of 0.998–0.999. For the NAFEMS T4 heat transfer benchmark, a 5.4% relative error is observed. The VQA converges robustly within 77–350 iterations, though barren plateaus are a known challenge for scaling to larger systems. This work establishes a scalable framework for quantum FEM, offering a significant memory advantage over classical methods and advancing the potential for quantum-enhanced engineering simulations.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"42 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146097947","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-30DOI: 10.1088/2058-9565/ae2202
Reyhaneh Aghaei Saem, Behrang Tafreshi, Zoë Holmes and Supanut Thanasilp
Identifying scalable circuit architectures remains a central challenge in variational quantum computing and quantum machine learning. Many approaches have been proposed to mitigate or avoid the barren plateau phenomenon or, more broadly, exponential concentration. However, due to the intricate interplay between quantum measurements and classical post-processing, we argue these techniques often fail to circumvent concentration effects in practice. Here, by analyzing concentration at the level of measurement outcome probabilities and leveraging tools from hypothesis testing, we develop a practical framework for diagnosing whether a parameterized quantum model is inhibited by exponential concentration. Applying this framework, we argue that several widely used methods (including quantum natural gradient, sample-based optimization, and certain neural-network-inspired initializations) do not overcome exponential concentration with finite measurement budgets, though they may still aid training in other ways.
{"title":"Pitfalls when tackling the exponential concentration of parameterized quantum models","authors":"Reyhaneh Aghaei Saem, Behrang Tafreshi, Zoë Holmes and Supanut Thanasilp","doi":"10.1088/2058-9565/ae2202","DOIUrl":"https://doi.org/10.1088/2058-9565/ae2202","url":null,"abstract":"Identifying scalable circuit architectures remains a central challenge in variational quantum computing and quantum machine learning. Many approaches have been proposed to mitigate or avoid the barren plateau phenomenon or, more broadly, exponential concentration. However, due to the intricate interplay between quantum measurements and classical post-processing, we argue these techniques often fail to circumvent concentration effects in practice. Here, by analyzing concentration at the level of measurement outcome probabilities and leveraging tools from hypothesis testing, we develop a practical framework for diagnosing whether a parameterized quantum model is inhibited by exponential concentration. Applying this framework, we argue that several widely used methods (including quantum natural gradient, sample-based optimization, and certain neural-network-inspired initializations) do not overcome exponential concentration with finite measurement budgets, though they may still aid training in other ways.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"44 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146072386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-29DOI: 10.1088/2058-9565/ae1e27
Steve Campbell, Irene D’Amico, Mario A Ciampini, Janet Anders, Natalia Ares, Simone Artini, Alexia Auffèves, Lindsay Bassman Oftelie, Laetitia P Bettmann, Marcus V S Bonança, Thomas Busch, Michele Campisi, Moallison F Cavalcante, Luis A Correa, Eloisa Cuestas, Ceren B Dag, Salambô Dago, Sebastian Deffner, Adolfo Del Campo, Andreas Deutschmann-Olek, Sandro Donadi, Emery Doucet, Cyril Elouard, Klaus Ensslin, Paul Erker, Nicole Fabbri, Federico Fedele, Guilherme Fiusa, Thomás Fogarty, Joshua Folk, Giacomo Guarnieri, Abhaya S Hegde, Santiago Hernández-Gómez, Chang-Kang Hu, Fernando Iemini, Bayan Karimi, Nikolai Kiesel, Gabriel T Landi, Aleksander Lasek, Sergei Lemziakov, Gabriele Lo Monaco, Eric Lutz, Dmitrii Lvov, Olivier Maillet, Mohammad Mehboudi, Taysa M Mendonça, Harry J D Miller, Andrew K Mitchell, Mark T Mitchison, Victor Mukherjee, Mauro Paternostro, Jukka Pekola, Martí Perarnau-Llobet, Ulrich Poschinger, Alberto Rolandi, Dario Rosa, Rafael Sánchez, Alan C Santos, Roberto..
The last two decades have seen quantum thermodynamics become a well established field of research in its own right. In that time, it has demonstrated a remarkably broad applicability, ranging from providing foundational advances in the understanding of how thermodynamic principles apply at the nano-scale and in the presence of quantum coherence, to providing a guiding framework for the development of efficient quantum devices. Exquisite levels of control have allowed state-of-the-art experimental platforms to explore energetics and thermodynamics at the smallest scales which has in turn helped to drive theoretical advances. This Roadmap provides an overview of the recent developments across many of the field’s sub-disciplines, assessing the key challenges and future prospects, providing a guide for its near term progress.
{"title":"Roadmap on quantum thermodynamics","authors":"Steve Campbell, Irene D’Amico, Mario A Ciampini, Janet Anders, Natalia Ares, Simone Artini, Alexia Auffèves, Lindsay Bassman Oftelie, Laetitia P Bettmann, Marcus V S Bonança, Thomas Busch, Michele Campisi, Moallison F Cavalcante, Luis A Correa, Eloisa Cuestas, Ceren B Dag, Salambô Dago, Sebastian Deffner, Adolfo Del Campo, Andreas Deutschmann-Olek, Sandro Donadi, Emery Doucet, Cyril Elouard, Klaus Ensslin, Paul Erker, Nicole Fabbri, Federico Fedele, Guilherme Fiusa, Thomás Fogarty, Joshua Folk, Giacomo Guarnieri, Abhaya S Hegde, Santiago Hernández-Gómez, Chang-Kang Hu, Fernando Iemini, Bayan Karimi, Nikolai Kiesel, Gabriel T Landi, Aleksander Lasek, Sergei Lemziakov, Gabriele Lo Monaco, Eric Lutz, Dmitrii Lvov, Olivier Maillet, Mohammad Mehboudi, Taysa M Mendonça, Harry J D Miller, Andrew K Mitchell, Mark T Mitchison, Victor Mukherjee, Mauro Paternostro, Jukka Pekola, Martí Perarnau-Llobet, Ulrich Poschinger, Alberto Rolandi, Dario Rosa, Rafael Sánchez, Alan C Santos, Roberto..","doi":"10.1088/2058-9565/ae1e27","DOIUrl":"https://doi.org/10.1088/2058-9565/ae1e27","url":null,"abstract":"The last two decades have seen quantum thermodynamics become a well established field of research in its own right. In that time, it has demonstrated a remarkably broad applicability, ranging from providing foundational advances in the understanding of how thermodynamic principles apply at the nano-scale and in the presence of quantum coherence, to providing a guiding framework for the development of efficient quantum devices. Exquisite levels of control have allowed state-of-the-art experimental platforms to explore energetics and thermodynamics at the smallest scales which has in turn helped to drive theoretical advances. This Roadmap provides an overview of the recent developments across many of the field’s sub-disciplines, assessing the key challenges and future prospects, providing a guide for its near term progress.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"33 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146070420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-29DOI: 10.1088/2058-9565/ae36cc
Jonathan Nemirovsky, Maya Chuchem and Yotam Shapira
As quantum processors grow in scale and reliability, the need for efficient quantum gate decomposition of circuits to a set of specific available gates, becomes ever more critical. The decomposition of a particular algorithm into a sequence of these available gates is not unique. Thus, the fidelity of an algorithm’s implementation can be increased by choosing an optimized decomposition. This is true both for noisy intermediate-scale quantum platforms as well as for implementation of quantum error correction schemes. Here we present a compilation scheme which implements a general-circuit decomposition to a sequence of Ising-type, long-range, multi-qubit (MQ) entangling gates, that are separated by layers of single qubit rotations. We use trapped ions as an example in which MQ gates naturally arise, yet any system that has connectivity beyond nearest-neighbors may gain from our approach. We evaluate our methods using the quantum volume (QV) test over N qubits. In this context, our method replaces two-qubit gates with MQ gates. Furthermore, our method minimizes the magnitude of the entanglement phases, which typically enables an improved implementation fidelity, by using weaker driving fields or faster realizations. We numerically test our compilation and show that, compared to conventional realizations with sequential two-qubit gates, our compilations improves the logarithm of QV by 20% to 25%.
{"title":"Efficient compilation of quantum circuits using multi-qubit gates","authors":"Jonathan Nemirovsky, Maya Chuchem and Yotam Shapira","doi":"10.1088/2058-9565/ae36cc","DOIUrl":"https://doi.org/10.1088/2058-9565/ae36cc","url":null,"abstract":"As quantum processors grow in scale and reliability, the need for efficient quantum gate decomposition of circuits to a set of specific available gates, becomes ever more critical. The decomposition of a particular algorithm into a sequence of these available gates is not unique. Thus, the fidelity of an algorithm’s implementation can be increased by choosing an optimized decomposition. This is true both for noisy intermediate-scale quantum platforms as well as for implementation of quantum error correction schemes. Here we present a compilation scheme which implements a general-circuit decomposition to a sequence of Ising-type, long-range, multi-qubit (MQ) entangling gates, that are separated by layers of single qubit rotations. We use trapped ions as an example in which MQ gates naturally arise, yet any system that has connectivity beyond nearest-neighbors may gain from our approach. We evaluate our methods using the quantum volume (QV) test over N qubits. In this context, our method replaces two-qubit gates with MQ gates. Furthermore, our method minimizes the magnitude of the entanglement phases, which typically enables an improved implementation fidelity, by using weaker driving fields or faster realizations. We numerically test our compilation and show that, compared to conventional realizations with sequential two-qubit gates, our compilations improves the logarithm of QV by 20% to 25%.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"117 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146070421","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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