Quantum最新文献_第9页

Transforming graph states via Bell state measurements 通过贝尔状态测量变换图形状态

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-07-14 DOI: 10.22331/q-2025-07-14-1795

Matthias C. Löbl, Love A. Pettersson, Stefano Paesani, Anders S. Sørensen

引用次数: 0

Unstructured Adiabatic Quantum Optimization: Optimality with Limitations 非结构绝热量子优化：有限制的最优性

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-07-11 DOI: 10.22331/q-2025-07-11-1790

Arthur Braida, Shantanav Chakraborty, Alapan Chaudhuri, Joseph Cunningham, Rutvij Menavlikar, Leonardo Novo, Jérémie Roland

{"title":"Unstructured Adiabatic Quantum Optimization: Optimality with Limitations","authors":"Arthur Braida, Shantanav Chakraborty, Alapan Chaudhuri, Joseph Cunningham, Rutvij Menavlikar, Leonardo Novo, Jérémie Roland","doi":"10.22331/q-2025-07-11-1790","DOIUrl":"https://doi.org/10.22331/q-2025-07-11-1790","url":null,"abstract":"In the circuit model of quantum computing, amplitude amplification techniques can be used to find solutions to NP-hard problems defined on $n$-bits in time $text{poly}(n) 2^{n/2}$. In this work, we investigate whether such general statements can be made for adiabatic quantum optimization, as provable results regarding its performance are mostly unknown. Although a lower bound of $Omega(2^{n/2})$ has existed in such a setting for over a decade, a purely adiabatic algorithm with this running time has been absent. We show that adiabatic quantum optimization using an unstructured search approach results in a running time that matches this lower bound (up to a polylogarithmic factor) for a broad class of classical local spin Hamiltonians. For this, it is necessary to bound the spectral gap throughout the adiabatic evolution and compute beforehand the position of the avoided crossing with sufficient precision so as to adapt the adiabatic schedule accordingly. However, we show that the position of the avoided crossing is approximately given by a quantity that depends on the degeneracies and inverse gaps of the problem Hamiltonian and is NP-hard to compute even within a low additive precision. Furthermore, computing it exactly (or nearly exactly) is #P-hard. Our work indicates a possible limitation of adiabatic quantum optimization algorithms, leaving open the question of whether provable Grover-like speed-ups can be obtained for any optimization problem using this approach.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"22 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144611346","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}

引用次数: 0

Quantum Enhanced Sensitivity through Many-Body Bloch Oscillations 通过多体布洛赫振荡量子增强灵敏度

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-07-11 DOI: 10.22331/q-2025-07-11-1793

Hassan Manshouri, Moslem Zarei, Mehdi Abdi, Sougato Bose, Abolfazl Bayat

{"title":"Quantum Enhanced Sensitivity through Many-Body Bloch Oscillations","authors":"Hassan Manshouri, Moslem Zarei, Mehdi Abdi, Sougato Bose, Abolfazl Bayat","doi":"10.22331/q-2025-07-11-1793","DOIUrl":"https://doi.org/10.22331/q-2025-07-11-1793","url":null,"abstract":"We investigate the sensing capacity of non-equilibrium dynamics in quantum systems exhibiting Bloch oscillations. By focusing on the resource efficiency of the probe, quantified by quantum Fisher information, we find different scaling behaviors in two different phases, namely localized and extended. Our results provide a quantitative ansatz for quantum Fisher information in terms of time, probe size, and the number of excitations. In the long-time regime, the quantum Fisher information is a quadratic function of time, touching the Heisenberg limit. The system size scaling drastically depends on the phase changing from quantum-enhanced scaling in the extended phase to size-independent behavior in the localized phase. Furthermore, increasing the number of excitations always enhances the precision of the probe, although, in the interacting systems the enhancement becomes less eminent than the non-interacting probes. This is due to the induced localization by increasing the interaction between the excitations. We show that a simple particle configuration measurement together with a maximum likelihood estimation can closely reach the ultimate precision limit in both single- and multi-particle probes.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"107 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144611350","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}

引用次数: 0

Quantum PCPs: on Adaptivity, Multiple Provers and Reductions to Local Hamiltonians 量子pcp：关于自适应、多重证明和局部哈密顿量的约简

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-07-11 DOI: 10.22331/q-2025-07-11-1791

Harry Buhrman, Jonas Helsen, Jordi Weggemans

{"title":"Quantum PCPs: on Adaptivity, Multiple Provers and Reductions to Local Hamiltonians","authors":"Harry Buhrman, Jonas Helsen, Jordi Weggemans","doi":"10.22331/q-2025-07-11-1791","DOIUrl":"https://doi.org/10.22331/q-2025-07-11-1791","url":null,"abstract":"We define a general formulation of quantum PCPs, which captures adaptivity and multiple unentangled provers, and give a detailed construction of the quantum reduction to a local Hamiltonian with a constant promise gap. The reduction turns out to be a versatile subroutine to prove properties of quantum PCPs, allowing us to show: (i) Non-adaptive quantum PCPs can simulate adaptive quantum PCPs when the number of proof queries is constant. In fact, this can even be shown to hold when the non-adaptive quantum PCP picks the proof indices simply uniformly at random from a subset of all possible index combinations, answering an open question by Aharonov, Arad, Landau and Vazirani (STOC '09). (ii) If the $q$-local Hamiltonian problem with constant promise gap can be solved in $mathsf{QCMA}$, then $mathsf{QPCP}[q] subseteq mathsf{QCMA}$ for any $q in O(1)$. (iii) If $mathsf{QMA}(k)$ has a quantum PCP for any $k leq text{poly}(n)$, then $mathsf{QMA}(2) = mathsf{QMA}$, connecting two of the longest-standing open problems in quantum complexity theory. Moreover, we also show that there exist (quantum) oracles relative to which certain quantum PCP statements are false. Hence, any attempt to prove the quantum PCP conjecture requires, just as was the case for the classical PCP theorem, (quantumly) non-relativizing techniques.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"1 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144611404","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}

引用次数: 0

Learning Feedback Mechanisms for Measurement-Based Variational Quantum State Preparation 基于测量的变分量子态制备的学习反馈机制

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-07-11 DOI: 10.22331/q-2025-07-11-1792

Daniel Alcalde Puente, Matteo Rizzi

{"title":"Learning Feedback Mechanisms for Measurement-Based Variational Quantum State Preparation","authors":"Daniel Alcalde Puente, Matteo Rizzi","doi":"10.22331/q-2025-07-11-1792","DOIUrl":"https://doi.org/10.22331/q-2025-07-11-1792","url":null,"abstract":"This work introduces a self-learning protocol that incorporates measurement and feedback into variational quantum circuits for efficient quantum state preparation. By combining projective measurements with conditional feedback, the protocol learns state preparation strategies that extend beyond unitary-only methods, leveraging measurement-based shortcuts to reduce circuit depth. Using the spin-1 Affleck-Kennedy-Lieb-Tasaki state as a benchmark, the protocol learns high-fidelity state preparation by overcoming a family of measurement induced local minima through adjustments of parameter update frequencies and ancilla regularization. Despite these efforts, optimization remains challenging due to the highly non-convex landscapes inherent to variational circuits. The approach is extended to larger systems using translationally invariant ansÃ¤tze and recurrent neural networks for feedback, demonstrating scalability. Additionally, the successful preparation of a specific AKLT state with desired edge modes highlights the potential to discover new state preparation protocols where none currently exist. These results indicate that integrating measurement and feedback into variational quantum algorithms provides a promising framework for quantum state preparation.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"37 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144611349","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}

引用次数: 0

Classical Simulation of High Temperature Quantum Ising Models 高温量子Ising模型的经典模拟

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-07-09 DOI: 10.22331/q-2025-07-09-1788

Elizabeth Crosson, Samuel Slezak

{"title":"Classical Simulation of High Temperature Quantum Ising Models","authors":"Elizabeth Crosson, Samuel Slezak","doi":"10.22331/q-2025-07-09-1788","DOIUrl":"https://doi.org/10.22331/q-2025-07-09-1788","url":null,"abstract":"We consider generalized quantum Ising models, including those which could describe disordered materials or quantum annealers, and we prove that for all temperatures above a system-size independent threshold the path integral Monte Carlo method based on worldline heat-bath updates always mixes to stationarity in time $mathcal{O}(n log n)$ for an $n$ qubit system, and therefore provides a fully polynomial-time approximation scheme for the partition function. This result holds whenever the temperature is greater than four plus twice the maximum interaction degree (valence) over all qubits, measured in units of the local coupling strength. For example, this implies that the classical simulation of the thermal state of a superconducting device modeling a frustrated quantum Ising model with maximum valence of 6 and coupling strengths of 1 GHz is always possible at temperatures above 800 mK. Despite the quantum system being at high temperature, the classical spin system resulting from the quantum-to-classical mapping contains strong couplings which cause the single-site Glauber dynamics to mix slowly, therefore this result depends on the use of worldline updates (which are a form of cluster updates that can be implemented efficiently). This result places definite constraints on the temperatures required for a quantum advantage in analog quantum simulation with various NISQ devices based on equilibrium states of quantum Ising models.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"9 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144594510","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}

引用次数: 0

Gauge freedoms in unravelled quantum dynamics: When do different continuous measurements yield identical quantum trajectories? 解开量子动力学中的规范自由：不同的连续测量何时产生相同的量子轨迹？

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-07-09 DOI: 10.22331/q-2025-07-09-1787

Calum A. Brown, Katarzyna Macieszczak, Robert L. Jack

{"title":"Gauge freedoms in unravelled quantum dynamics: When do different continuous measurements yield identical quantum trajectories?","authors":"Calum A. Brown, Katarzyna Macieszczak, Robert L. Jack","doi":"10.22331/q-2025-07-09-1787","DOIUrl":"https://doi.org/10.22331/q-2025-07-09-1787","url":null,"abstract":"Quantum trajectories of a Markovian open quantum system arise from the back-action of measurements performed in the environment with which the system interacts. In this work, we consider counting measurements of quantum jumps, corresponding to different representations of the same quantum master equation. We derive necessary and sufficient conditions under which these different measurements give rise to the same unravelled quantum master equation, which governs the dynamics of the probability distribution over pure conditional states of the system. Since that equation uniquely determines the stochastic dynamics of a conditional state, we also obtain necessary and sufficient conditions under which different measurements result in identical quantum trajectories. We then consider the joint stochastic dynamics for the conditional state and the measurement record. We formulate this in terms of labelled quantum trajectories, and derive necessary and sufficient conditions under which different representations lead to equivalent labelled quantum trajectories, up to permutations of labels. As those conditions are generally stricter, we finish by constructing coarse-grained measurement records, such that equivalence of the corresponding partially-labelled trajectories is guaranteed by equivalence of the trajectories alone. These general results are illustrated by two examples that demonstrate permutation of labels, and equivalence of different quantum trajectories.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"10 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144594562","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}

引用次数: 0

Deep Circuit Compression for Quantum Dynamics via Tensor Networks 基于张量网络的量子动力学深度电路压缩

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-07-09 DOI: 10.22331/q-2025-07-09-1789

Joe Gibbs, Lukasz Cincio

引用次数: 0

Quantum state preparation via piecewise QSVT 通过分段QSVT制备量子态

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-07-03 DOI: 10.22331/q-2025-07-03-1786

Oliver O'Brien, Christoph Sünderhauf

引用次数: 0

Sampling Groups of Pauli Operators to Enhance Direct Fidelity Estimation 泡利算子的抽样群提高直接保真度估计