Pub Date : 2026-02-12DOI: 10.1088/2058-9565/ae3f4e
ZhiXin Xia, SiYing Wang, Yue Yan and Xiang-Bin Wang
Achieving large-scale real-time decoding requires efficient and accurate decoders. However, conventional decoding strategies for surface codes struggle to balance speed with accuracy. In this work, we propose the adaptive decision-making (ADM) strategy, which optimizes the local decisions through intermediate information during the decoding process, while maintaining rapid decoding. We compare the performance of different real-time strategies by integrating them into the union-find (UF) decoding framework. Numerical simulations under different noises show that our ADM-UF decoder significantly improves the threshold, outperforming its highly relevant competitors. Empirical evidence confirms that ADM-UF achieves an almost-linear complexity, ensuring real-time decoding for large-scale quantum codes. These results validate the efficacy of our ADM strategy.
{"title":"The adaptive decision-making strategy for surface code decoding","authors":"ZhiXin Xia, SiYing Wang, Yue Yan and Xiang-Bin Wang","doi":"10.1088/2058-9565/ae3f4e","DOIUrl":"https://doi.org/10.1088/2058-9565/ae3f4e","url":null,"abstract":"Achieving large-scale real-time decoding requires efficient and accurate decoders. However, conventional decoding strategies for surface codes struggle to balance speed with accuracy. In this work, we propose the adaptive decision-making (ADM) strategy, which optimizes the local decisions through intermediate information during the decoding process, while maintaining rapid decoding. We compare the performance of different real-time strategies by integrating them into the union-find (UF) decoding framework. Numerical simulations under different noises show that our ADM-UF decoder significantly improves the threshold, outperforming its highly relevant competitors. Empirical evidence confirms that ADM-UF achieves an almost-linear complexity, ensuring real-time decoding for large-scale quantum codes. These results validate the efficacy of our ADM strategy.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"32 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146160140","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 : 2026-02-11DOI: 10.1088/2058-9565/ae3a13
Eleftherios Mastorakis, Muhammad Umer, Milena Guevara-Bertsch, Juris Ulmanis, Felix Rohde and Dimitris G Angelakis
Resource-efficient, low-depth implementations of quantum circuits remain a promising strategy for achieving reliable and scalable computation on quantum hardware, as they reduce gate resources and limit the accumulation of noisy operations. Here, we propose a low-depth implementation of a class of Hadamard test circuits, complemented by the development of a parameterized quantum ansatz specifically tailored for variational algorithms that exploit the underlying Hadamard test framework. Our findings demonstrate a significant reduction in single- and two-qubit gate counts, suggesting a reliable circuit architecture for noisy intermediate-scale quantum devices. Building on this foundation, we tested our low-depth scheme to investigate the expressive capacity of the proposed parameterized ansatz in simulating nonlinear Burgers’ dynamics. The resulting variational quantum states faithfully capture the shockwave feature of the turbulent regime and maintain high overlaps with classical benchmarks, underscoring the practical effectiveness of our framework. Furthermore, we evaluate the effect of hardware noise by modeling the error properties of real quantum processors and by executing the variational algorithm on a trapped-ion-based IBEX Q1 device. The outcomes of our demonstrations highlight the resilience of our low-depth scheme in the turbulent regime, consistently preparing high-fidelity variational states that exhibit strong agreement with classical benchmarks. Our work contributes to the advancement of resource-efficient strategies for quantum computation, offering a robust framework for tackling a range of computationally intensive problems across numerous applications.
{"title":"Resource-efficient Hadamard test tailored variational framework for nonlinear dynamics on quantum computers","authors":"Eleftherios Mastorakis, Muhammad Umer, Milena Guevara-Bertsch, Juris Ulmanis, Felix Rohde and Dimitris G Angelakis","doi":"10.1088/2058-9565/ae3a13","DOIUrl":"https://doi.org/10.1088/2058-9565/ae3a13","url":null,"abstract":"Resource-efficient, low-depth implementations of quantum circuits remain a promising strategy for achieving reliable and scalable computation on quantum hardware, as they reduce gate resources and limit the accumulation of noisy operations. Here, we propose a low-depth implementation of a class of Hadamard test circuits, complemented by the development of a parameterized quantum ansatz specifically tailored for variational algorithms that exploit the underlying Hadamard test framework. Our findings demonstrate a significant reduction in single- and two-qubit gate counts, suggesting a reliable circuit architecture for noisy intermediate-scale quantum devices. Building on this foundation, we tested our low-depth scheme to investigate the expressive capacity of the proposed parameterized ansatz in simulating nonlinear Burgers’ dynamics. The resulting variational quantum states faithfully capture the shockwave feature of the turbulent regime and maintain high overlaps with classical benchmarks, underscoring the practical effectiveness of our framework. Furthermore, we evaluate the effect of hardware noise by modeling the error properties of real quantum processors and by executing the variational algorithm on a trapped-ion-based IBEX Q1 device. The outcomes of our demonstrations highlight the resilience of our low-depth scheme in the turbulent regime, consistently preparing high-fidelity variational states that exhibit strong agreement with classical benchmarks. Our work contributes to the advancement of resource-efficient strategies for quantum computation, offering a robust framework for tackling a range of computationally intensive problems across numerous applications.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"97 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146153360","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 : 2026-02-10DOI: 10.1088/2058-9565/ae3fc8
Chenyu Shi, Vedran Dunjko and Hao Wang
The variational quantum eigensolver (VQE) is one of the most prominent algorithms using near-term quantum devices, designed to find the ground state of a Hamiltonian. In VQE, a classical optimizer iteratively updates the parameters in the quantum circuit. Among various optimization methods, the quantum natural gradient descent (QNG) stands out as a promising optimization approach for VQE. However, standard QNG only leverages the quantum Fisher information of the entire system and treats each subsystem equally in the optimization process, without accounting for the different weights and contributions of each subsystem corresponding to each local term in the Hamiltonian. To address this limitation, we propose a Weighted Approximate QNG (WA-QNG) method tailored for k-local Hamiltonians. In this paper, we theoretically analyze the potential advantages of WA-QNG compared to QNG from three distinct perspectives and reveal its connection with the Gauss–Newton method. We also show it outperforms the standard QNG descent in the numerical simulations for seeking the ground state of the Hamiltonian.
{"title":"Weighted approximate quantum natural gradient for variational quantum eigensolver","authors":"Chenyu Shi, Vedran Dunjko and Hao Wang","doi":"10.1088/2058-9565/ae3fc8","DOIUrl":"https://doi.org/10.1088/2058-9565/ae3fc8","url":null,"abstract":"The variational quantum eigensolver (VQE) is one of the most prominent algorithms using near-term quantum devices, designed to find the ground state of a Hamiltonian. In VQE, a classical optimizer iteratively updates the parameters in the quantum circuit. Among various optimization methods, the quantum natural gradient descent (QNG) stands out as a promising optimization approach for VQE. However, standard QNG only leverages the quantum Fisher information of the entire system and treats each subsystem equally in the optimization process, without accounting for the different weights and contributions of each subsystem corresponding to each local term in the Hamiltonian. To address this limitation, we propose a Weighted Approximate QNG (WA-QNG) method tailored for k-local Hamiltonians. In this paper, we theoretically analyze the potential advantages of WA-QNG compared to QNG from three distinct perspectives and reveal its connection with the Gauss–Newton method. We also show it outperforms the standard QNG descent in the numerical simulations for seeking the ground state of the Hamiltonian.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"11 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146146192","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 : 2026-02-10DOI: 10.1088/2058-9565/ae3b6e
Jin-Min Liang, Shuheng Liu, Shao-Ming Fei and Qiongyi He
The characterization of high-dimensional entanglement plays a crucial role in the field of quantum information science. Conventional entanglement criteria measuring coherent superpositions of multiple basis states face experimental bottlenecks on most physical platforms due to limited multi-channel control. Here, we introduce a practically efficient detection strategy based on randomized product projections. We show that the first-order moments of such projections can be used to estimate entanglement fidelity, thereby enabling practical and efficient certification of the Schmidt number (SN) in high-dimensional bipartite systems. By constructing optimal observables, it is sufficient to merely measure a single basis state, substantially reducing experimental overhead. Moreover, we present an algorithm to obtain a lower bound of the SN with a high confidence level from a limited number of experimental data. Our results open up resource-efficient experimental avenues to detect high-dimensional entanglement and test its implementations in modern information technologies.
{"title":"Detecting high-dimensional entanglement by randomized product projections","authors":"Jin-Min Liang, Shuheng Liu, Shao-Ming Fei and Qiongyi He","doi":"10.1088/2058-9565/ae3b6e","DOIUrl":"https://doi.org/10.1088/2058-9565/ae3b6e","url":null,"abstract":"The characterization of high-dimensional entanglement plays a crucial role in the field of quantum information science. Conventional entanglement criteria measuring coherent superpositions of multiple basis states face experimental bottlenecks on most physical platforms due to limited multi-channel control. Here, we introduce a practically efficient detection strategy based on randomized product projections. We show that the first-order moments of such projections can be used to estimate entanglement fidelity, thereby enabling practical and efficient certification of the Schmidt number (SN) in high-dimensional bipartite systems. By constructing optimal observables, it is sufficient to merely measure a single basis state, substantially reducing experimental overhead. Moreover, we present an algorithm to obtain a lower bound of the SN with a high confidence level from a limited number of experimental data. Our results open up resource-efficient experimental avenues to detect high-dimensional entanglement and test its implementations in modern information technologies.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"92 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146146191","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 : 2026-02-05DOI: 10.1088/2058-9565/ae34e0
Vinicius F Lisboa, Pedro R Dieguez, Kyrylo Simonov and Roberto M Serra
Allowing the order of quantum operations to exist in superposition is known to open new routes for thermodynamic tasks. We investigate a quantum heat engine where energy exchanges are driven by generalized measurements, and the sequence of these operations is coherently controlled in a superposition of causal orders. Our analysis explores how initial correlations between the working medium and the controller affect the engine’s performance. Considering uncorrelated, classically correlated, and entangled initial states, we show that entanglement enables the superposed causal order (SCO) to generate coherence in the working medium, thereby enhancing work extraction and efficiency beyond the separable and uncorrelated cases. Finally, we present a proof-of-principle simulation on the IBM Quantum Experience platform, realizing a quantum switch of two measurement channels with tunable strengths and experimentally confirming the predicted efficiency enhancement enabled by correlation-assisted SCO.
{"title":"Correlations in a quantum switch-based heat engine with measurements: a proof-of-principle demonstration","authors":"Vinicius F Lisboa, Pedro R Dieguez, Kyrylo Simonov and Roberto M Serra","doi":"10.1088/2058-9565/ae34e0","DOIUrl":"https://doi.org/10.1088/2058-9565/ae34e0","url":null,"abstract":"Allowing the order of quantum operations to exist in superposition is known to open new routes for thermodynamic tasks. We investigate a quantum heat engine where energy exchanges are driven by generalized measurements, and the sequence of these operations is coherently controlled in a superposition of causal orders. Our analysis explores how initial correlations between the working medium and the controller affect the engine’s performance. Considering uncorrelated, classically correlated, and entangled initial states, we show that entanglement enables the superposed causal order (SCO) to generate coherence in the working medium, thereby enhancing work extraction and efficiency beyond the separable and uncorrelated cases. Finally, we present a proof-of-principle simulation on the IBM Quantum Experience platform, realizing a quantum switch of two measurement channels with tunable strengths and experimentally confirming the predicted efficiency enhancement enabled by correlation-assisted SCO.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"33 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146115592","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 : 2026-02-05DOI: 10.1088/2058-9565/ae2e39
Sofia Sevitz, Federico Cerisola, Karen V Hovhannisyan and Janet Anders
Particle-exchange machines utilize electronic transport to continuously transfer heat between fermionic reservoirs. Here, we introduce a model coupling a quantum mechanical resonator to a particle-exchange machine hosted in a quantum dot (QD) and let the system run autonomously. This way, part of the energy exchanged between the reservoirs can be stored in the resonator in the form of self-oscillations. Our analysis goes well beyond previous works by exploring the slow transport regime and accessing arbitrarily strong dot–resonator coupling. First, we introduce a faithful measure of self-oscillations, and use it to certify that they can occur in the slow-transport regime. We furthermore show that the electrical current through the dot can be used to witness self-oscillations. Finally, we establish that, under realistic conditions, self-oscillations occur only when the machine operates as a heater. We define an experimentally measurable performance metric characterizing the efficiency of current–to–self-oscillations conversion. It reveals that, counterintuitively, strong dot–resonator coupling is detrimental to the conversion performance. The framework developed here can be readily implemented in a variety of nanoscale devices, such as a suspended carbon nanotube with an embedded QD.
{"title":"Autonomous conversion of particle-exchange to quantum self-oscillations","authors":"Sofia Sevitz, Federico Cerisola, Karen V Hovhannisyan and Janet Anders","doi":"10.1088/2058-9565/ae2e39","DOIUrl":"https://doi.org/10.1088/2058-9565/ae2e39","url":null,"abstract":"Particle-exchange machines utilize electronic transport to continuously transfer heat between fermionic reservoirs. Here, we introduce a model coupling a quantum mechanical resonator to a particle-exchange machine hosted in a quantum dot (QD) and let the system run autonomously. This way, part of the energy exchanged between the reservoirs can be stored in the resonator in the form of self-oscillations. Our analysis goes well beyond previous works by exploring the slow transport regime and accessing arbitrarily strong dot–resonator coupling. First, we introduce a faithful measure of self-oscillations, and use it to certify that they can occur in the slow-transport regime. We furthermore show that the electrical current through the dot can be used to witness self-oscillations. Finally, we establish that, under realistic conditions, self-oscillations occur only when the machine operates as a heater. We define an experimentally measurable performance metric characterizing the efficiency of current–to–self-oscillations conversion. It reveals that, counterintuitively, strong dot–resonator coupling is detrimental to the conversion performance. The framework developed here can be readily implemented in a variety of nanoscale devices, such as a suspended carbon nanotube with an embedded QD.","PeriodicalId":20821,"journal":{"name":"Quantum Science and Technology","volume":"115 1","pages":""},"PeriodicalIF":6.7,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146115593","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 : 2026-02-05DOI: 10.1088/2058-9565/ae3e3b
Nikita Guseynov, Xiajie Huang and Nana Liu
We propose an explicit quantum framework for numerically simulating general linear partial differential equations (PDEs), extending previous work (Guseynov et al 2025 Phys. Rev. Res.7 033100) to incorporate (a) Robin boundary conditions—which include Neumann and Dirichlet conditions as special cases–(b) inhomogeneous terms, and (c) variable coefficients in space and time. Our approach begins with a general finite-difference discretization and applies the Schrödingerisation technique to transform the resulting system into one that admits unitary quantum evolution, enabling quantum simulation. For the Schrödinger equation corresponding to the discretized PDE, we construct an efficient block-encoding of the Hamiltonian H that scales polylogarithmically with the number of grid points N. This encoding is compatible with quantum signal processing and allows for the implementation of the evolution operator . The explicit circuit construction in our method permits complexity to be measured in fundamental gate units–namely, CNOT gates and single-qubit rotations–bypassing the inefficiencies of oracle queries. Consequently, the overall algorithm scales polynomially with N and linearly with the spatial dimension d. Under certain input/output assumptions our method achieves a polynomial speedup in N and an exponential advantage in d for a wide class of PDEs, thereby mitigating the classical curse of dimensionality. The validity and efficiency of the proposed approach are further substantiated by numerical simulations. By explicitly defining the quantum operations and quantifying their resource requirements, our approach offers a practical alternative for numerically solving PDEs, distinct from others that rely on oracle queries and purely asymptotic scaling methods.
我们提出了一个显式的量子框架，用于数值模拟一般线性偏微分方程（PDEs），扩展了以前的工作（Guseynov et al . 2025）。Rev. Res.7 033100)纳入(a) Robin边界条件-其中包括Neumann和Dirichlet条件作为特殊情况- (b)非齐次项，以及(c)空间和时间中的可变系数。我们的方法从一般有限差分离散化开始，并应用Schrödingerisation技术将结果系统转换为允许单一量子演化的系统，从而实现量子模拟。对于对应于离散PDE的Schrödinger方程，我们构建了一个有效的哈密顿H的块编码，该编码与网格点n的数量成多对数比例。这种编码与量子信号处理兼容，并允许实现进化算子。我们方法中的显式电路结构允许用基本门单元（即CNOT门和单量子比特旋转）来测量复杂性，从而绕过了oracle查询的低效率。因此，整个算法随N多项式扩展，随空间维数d线性扩展。在特定的输入/输出假设下，我们的方法在N上实现了多项式加速，在d上实现了指数优势，从而减轻了经典的维数诅咒。数值仿真进一步验证了该方法的有效性和有效性。通过显式地定义量子操作和量化它们的资源需求，我们的方法为数值解决偏微分方程提供了一个实用的替代方案，不同于其他依赖于oracle查询和纯渐近缩放方法的方法。
{"title":"Quantum framework for simulating linear PDEs with Robin boundary conditions","authors":"Nikita Guseynov, Xiajie Huang and Nana Liu","doi":"10.1088/2058-9565/ae3e3b","DOIUrl":"https://doi.org/10.1088/2058-9565/ae3e3b","url":null,"abstract":"We propose an explicit quantum framework for numerically simulating general linear partial differential equations (PDEs), extending previous work (Guseynov et al 2025 Phys. Rev. Res.7 033100) to incorporate (a) Robin boundary conditions—which include Neumann and Dirichlet conditions as special cases–(b) inhomogeneous terms, and (c) variable coefficients in space and time. Our approach begins with a general finite-difference discretization and applies the Schrödingerisation technique to transform the resulting system into one that admits unitary quantum evolution, enabling quantum simulation. For the Schrödinger equation corresponding to the discretized PDE, we construct an efficient block-encoding of the Hamiltonian H that scales polylogarithmically with the number of grid points N. This encoding is compatible with quantum signal processing and allows for the implementation of the evolution operator . The explicit circuit construction in our method permits complexity to be measured in fundamental gate units–namely, CNOT gates and single-qubit rotations–bypassing the inefficiencies of oracle queries. Consequently, the overall algorithm scales polynomially with N and linearly with the spatial dimension d. Under certain input/output assumptions our method achieves a polynomial speedup in N and an exponential advantage in d for a wide class of PDEs, thereby mitigating the classical curse of dimensionality. The validity and efficiency of the proposed approach are further substantiated by numerical simulations. By explicitly defining the quantum operations and quantifying their resource requirements, our approach offers a practical alternative for numerically solving PDEs, distinct from others that rely on oracle queries and purely asymptotic scaling methods.","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":"146115716","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 : 2026-02-05DOI: 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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：