Quantum最新文献 - Book学术

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

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-07-03 DOI: 10.22331/q-2025-07-03-1784

Júlia Barberà-Rodríguez, Mariana Navarro, Leonardo Zambrano

引用次数: 0

Indefinite Time Directed Quantum Metrology 不定时间定向量子计量学

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-07-03 DOI: 10.22331/q-2025-07-03-1785

Gaurang Agrawal, Pritam Halder, Aditi SenDe

{"title":"Indefinite Time Directed Quantum Metrology","authors":"Gaurang Agrawal, Pritam Halder, Aditi SenDe","doi":"10.22331/q-2025-07-03-1785","DOIUrl":"https://doi.org/10.22331/q-2025-07-03-1785","url":null,"abstract":"We explore the performance of the metrology scheme by employing a quantum time flip during encoding, a specific case of processes with indefinite time direction, which we refer to as indefinite time directed metrology ($ITDM$). In the case of single parameter estimation of a unitary, we demonstrate that our protocol can achieve Heisenberg scaling $(1/N)$ with product probe states, surpassing the standard quantum limit $(1/{sqrt{N}})$, where $N$ is the number of particles in the probe. We establish this by computing the quantum Fisher information ($QFI$) which is a lower bound on the root mean square error occurred during parameter estimation. Although we analytically prove the optimality of the symmetric product probe state in $ITDM$, entangled probe states produce a higher $QFI$ than optimal product probes without enhancing scaling, highlighting the non-essentiality of entanglement. For phase estimation, we propose a single-qubit measurement on the control qubit that accomplishes near-optimal Fisher information and eventually reaches Heisenberg scaling. Our findings reveal the best orientation of product probe states in every pertinent situation, emphasizing its independence from the parameter to be estimated in the limiting case. Furthermore, we illustrate the benefits of $ITDM$ in noisy metrology, outperforming existing techniques in some situations.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"5 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144547524","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

Logical Noise Bias in Magic State Injection 魔态注入中的逻辑噪声偏差

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-06-24 DOI: 10.22331/q-2025-06-24-1779

Nicholas Fazio, Robin Harper, Stephen D. Bartlett

引用次数: 0

On the composable security of weak coin flipping 弱抛硬币的可组合安全性

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-06-24 DOI: 10.22331/q-2025-06-24-1780

Jiawei Wu, Yanglin Hu, Akshay Bansal, Marco Tomamichel

引用次数: 0

Breakdown of Measurement-Induced Phase Transitions Under Information Loss 信息损失下测量诱发相变的击穿

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-06-24 DOI: 10.22331/q-2025-06-24-1781

Alessio Paviglianiti, Giovanni Di Fresco, Alessandro Silva, Bernardo Spagnolo, Davide Valenti, Angelo Carollo

{"title":"Breakdown of Measurement-Induced Phase Transitions Under Information Loss","authors":"Alessio Paviglianiti, Giovanni Di Fresco, Alessandro Silva, Bernardo Spagnolo, Davide Valenti, Angelo Carollo","doi":"10.22331/q-2025-06-24-1781","DOIUrl":"https://doi.org/10.22331/q-2025-06-24-1781","url":null,"abstract":"The dynamics of a quantum-many body system subject to measurements is naturally described by an ensemble of quantum trajectories, which can feature measurement-induced phase transitions (MIPTs). This phenomenon cannot be revealed through ensemble-averaged observables, but it requires the ability to discriminate each trajectory separately, making its experimental observation extremely challenging. We explore the fate of MIPTs under an observer's reduced ability to discriminate each measurement outcome. This introduces uncertainty in the state of the system, causing observables to probe a restricted subset of trajectories rather than a single one. By introducing an exactly-solvable Liouvillian model, we examine how long-time spatial correlations are influenced by varying degrees of trajectory averaging. We compute exactly the correlation matrix, Liouvillian gap, and entanglement negativity to demonstrate that averaging over multiple realizations introduces an effective finite lengthscale, beyond which long-range correlations are suppressed. This suggests that partial averaging over trajectories conceals the critical features of individual realizations, thereby blurring away the signatures of distinct measurement-induced phases.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"50 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144370456","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

Subsystem Information Capacity in Random Circuits and Hamiltonian Dynamics 随机电路中的子系统信息容量与哈密顿动力学

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-06-24 DOI: 10.22331/q-2025-06-24-1783

Yu-Qin Chen, Shuo Liu, Shi-Xin Zhang

{"title":"Subsystem Information Capacity in Random Circuits and Hamiltonian Dynamics","authors":"Yu-Qin Chen, Shuo Liu, Shi-Xin Zhang","doi":"10.22331/q-2025-06-24-1783","DOIUrl":"https://doi.org/10.22331/q-2025-06-24-1783","url":null,"abstract":"In this study, we explore the information capacity of open quantum systems, focusing on the effective channels formed by the subsystem of random quantum circuits and quantum Hamiltonian evolution. By analyzing the subsystem information capacity, which is closely linked to quantum coherent information of these effective quantum channels, we uncover a diverse range of dynamical and steady behaviors depending on the types of evolution. Therefore, the subsystem information capacity serves as a valuable tool for studying the intrinsic nature of various dynamical phases, such as integrable, localized, thermalized, and topological systems. We also reveal the impact of different initial information encoding schemes on information dynamics including one-to-one, one-to-many, and many-to-many. To support our findings, we provide representative examples for numerical simulations, including random quantum circuits with or without mid-circuit measurements, random Clifford Floquet circuits, free and interacting Aubry-Andre models, and Su-Schrieffer-Heeger models. These numerical results are further quantitatively explained using the effective statistical model mapping and the quasiparticle picture in the cases of random circuits and non-interacting Hamiltonian dynamics, respectively.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"45 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144370475","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

Stabilizer ground states for simulating quantum many-body physics: theory, algorithms, and applications 用于模拟量子多体物理的稳定基态：理论、算法和应用

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-06-24 DOI: 10.22331/q-2025-06-24-1782

Jiace Sun, Lixue Cheng, Shi-Xin Zhang

引用次数: 0

Characterizing maximally many-body entangled fermionic states by using $M$-body density matrix 用M体密度矩阵刻画最大多体纠缠费米子态

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-06-24 DOI: 10.22331/q-2025-06-24-1778

Irakli Giorgadze, Haixuan Huang, Jordan Gaines, Elio J. König, Jukka I. Väyrynen

{"title":"Characterizing maximally many-body entangled fermionic states by using $M$-body density matrix","authors":"Irakli Giorgadze, Haixuan Huang, Jordan Gaines, Elio J. König, Jukka I. Väyrynen","doi":"10.22331/q-2025-06-24-1778","DOIUrl":"https://doi.org/10.22331/q-2025-06-24-1778","url":null,"abstract":"Fermionic Hamiltonians play a critical role in quantum chemistry, one of the most promising use cases for near-term quantum computers. However, since encoding nonlocal fermionic statistics using conventional qubits results in significant computational overhead, fermionic quantum hardware, such as fermion atom arrays, were proposed as a more efficient platform. In this context, we here study the many-body entanglement structure of fermionic $N$-particle states by concentrating on $M$-body reduced density matrices (DMs) across various bipartitions in Fock space. The von Neumann entropy of the reduced DM is a basis independent entanglement measure which generalizes the traditional quantum chemistry concept of the one-particle DM entanglement, which characterizes how a single fermion is entangled with the rest. We carefully examine upper bounds on the $M$-body entanglement, which are analogous to the volume law of conventional entanglement measures. To this end we establish a connection between $M$-body reduced DM and the mathematical structure of hypergraphs. Specifically, we show that a special class of hypergraphs, known as $t$-designs, corresponds to maximally entangled fermionic states. Finally, we explore fermionic many-body entanglement in random states. We semianalytically demonstrate that the distribution of reduced DMs associated with random fermionic states corresponds to the trace-fixed Wishart-Laguerre random matrix ensemble. In the limit of large single-particle dimension $D$ and a non-zero filling fraction, random states asymptotically become absolutely maximally entangled.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"25 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144370458","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

Improved Quantum Query Upper Bounds Based on Classical Decision Trees 基于经典决策树的改进量子查询上界

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-06-23 DOI: 10.22331/q-2025-06-23-1777

Arjan Cornelissen, Nikhil S. Mande, Subhasree Patro

{"title":"Improved Quantum Query Upper Bounds Based on Classical Decision Trees","authors":"Arjan Cornelissen, Nikhil S. Mande, Subhasree Patro","doi":"10.22331/q-2025-06-23-1777","DOIUrl":"https://doi.org/10.22331/q-2025-06-23-1777","url":null,"abstract":"Given a classical query algorithm as a decision tree, when does there exist a quantum query algorithm with a speed-up over the classical one? We provide a general construction based on the structure of the underlying decision tree, and prove that this can give us an up-to-quadratic quantum speed-up. In particular, we obtain a bounded-error quantum query algorithm of cost $O(sqrt{s})$ to compute a Boolean function (more generally, a relation) that can be computed by a classical (even randomized) decision tree of size $s$.<br/> Lin and Lin [ToC'16] and Beigi and Taghavi [Quantum'20] showed results of a similar flavor, and gave upper bounds in terms of a quantity which we call the \"guessing complexity\" of a decision tree. We identify that the guessing complexity of a decision tree equals its rank, a notion introduced by Ehrenfeucht and Haussler [Inf. Comp.'89] in the context of learning theory. This answers a question posed by Lin and Lin, who asked whether the guessing complexity of a decision tree is related to any complexity-theoretic measure. We also show a polynomial separation between rank and randomized rank for the complete binary AND-OR tree.<br/> Beigi and Taghavi constructed span programs and dual adversary solutions for Boolean functions given classical decision trees computing them and an assignment of non-negative weights to its edges. We explore the effect of changing these weights on the resulting span program complexity and objective value of the dual adversary bound, and capture the best possible weighting scheme by an optimization program. We exhibit a solution to this program and argue its optimality from first principles. We also exhibit decision trees for which our bounds are asymptotically stronger than those of Lin and Lin, and Beigi and Taghavi. This answers a question of Beigi and Taghavi, who asked whether different weighting schemes could yield better upper bounds.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"640 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144370455","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