Quantum最新文献_第4页

Impact of decoherence on the fidelity of quantum gates leaving the computational subspace

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-03 DOI: 10.22331/q-2025-04-03-1684

Tahereh Abad, Yoni Schattner, Anton Frisk Kockum, Göran Johansson

引用次数: 0

Which features of quantum physics are not fundamentally quantum but are due to indeterminism?

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-03 DOI: 10.22331/q-2025-04-03-1686

Flavio Del Santo, Nicolas Gisin

引用次数: 0

Learning in Quantum Common-Interest Games and the Separability Problem 量子共同利益博弈中的学习与可分性问题

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-03 DOI: 10.22331/q-2025-04-03-1689

Wayne Lin, Georgios Piliouras, Ryann Sim, Antonios Varvitsiotis

{"title":"Learning in Quantum Common-Interest Games and the Separability Problem","authors":"Wayne Lin, Georgios Piliouras, Ryann Sim, Antonios Varvitsiotis","doi":"10.22331/q-2025-04-03-1689","DOIUrl":"https://doi.org/10.22331/q-2025-04-03-1689","url":null,"abstract":"Learning in games has emerged as a powerful tool for machine learning with numerous applications. Quantum games model interactions between strategic players who have access to quantum resources, and several recent works have studied learning in the competitive regime of quantum zero-sum games. Going beyond this setting, we introduce quantum common-interest games (CIGs) where players have density matrices as strategies and their interests are perfectly aligned. We bridge the gap between optimization and game theory by establishing the equivalence between KKT (first-order stationary) points of an instance of the Best Separable State (BSS) problem and the Nash equilibria of its corresponding quantum CIG. This allows learning dynamics for the quantum CIG to be seen as decentralized algorithms for the BSS problem. Taking the perspective of learning in games, we then introduce non-commutative extensions of the continuous-time replicator dynamics and the discrete-time best response dynamics/linear multiplicative weights update for learning in quantum CIGs. We prove analogues of classical convergence results of the dynamics and explore differences which arise in the quantum setting. Finally, we corroborate our theoretical findings through extensive experiments.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"38 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143775663","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 Merlin-Arthur proof systems for synthesizing quantum states 用于合成量子态的量子梅林-阿瑟证明系统

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-03 DOI: 10.22331/q-2025-04-03-1688

Hugo Delavenne, François Le Gall, Yupan Liu, Masayuki Miyamoto

{"title":"Quantum Merlin-Arthur proof systems for synthesizing quantum states","authors":"Hugo Delavenne, François Le Gall, Yupan Liu, Masayuki Miyamoto","doi":"10.22331/q-2025-04-03-1688","DOIUrl":"https://doi.org/10.22331/q-2025-04-03-1688","url":null,"abstract":"Complexity theory typically focuses on the difficulty of solving computational problems using classical inputs and outputs, even with a quantum computer. In the quantum world, it is natural to apply a different notion of complexity, namely the complexity of synthesizing quantum states. We investigate a state-synthesizing counterpart of the class $sf{NP}$, referred to as $sf{stateQMA}$, which is concerned with preparing certain quantum states through a polynomial-time quantum verifier with the aid of a single quantum message from an all-powerful but untrusted prover. This is a subclass of the class $sf{stateQIP}$ recently introduced by Rosenthal and Yuen (ITCS 2022) [57], which permits polynomially many interactions between the prover and the verifier. Our main result consists of error reduction of this class and its variants with an exponentially small gap or bounded space, as well as how this class relates to other fundamental state synthesizing classes, i.e., states generated by uniform polynomial-time quantum circuits ($sf{stateBQP}$) and space-uniform polynomial-space quantum circuits ($sf{statePSPACE}$). Furthermore, we establish that the family of $sf{UQMA}$ witnesses, considered as one of the most natural candidates for $sf{stateQMA}$ containments, is in $sf{stateQMA}$. Additionally, we demonstrate that $sf{stateQCMA}$ achieves perfect completeness.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"26 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143775662","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

Free fermions under adaptive quantum dynamics 自适应量子动力学下的自由费米子

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-03 DOI: 10.22331/q-2025-04-03-1685

Vikram Ravindranath, Zhi-Cheng Yang, Xiao Chen

{"title":"Free fermions under adaptive quantum dynamics","authors":"Vikram Ravindranath, Zhi-Cheng Yang, Xiao Chen","doi":"10.22331/q-2025-04-03-1685","DOIUrl":"https://doi.org/10.22331/q-2025-04-03-1685","url":null,"abstract":"We study free fermion systems under adaptive quantum dynamics consisting of unitary gates and projective measurements followed by corrective unitary operations. We further introduce a classical flag for each site, allowing for an active or inactive status which determines whether or not the unitary gates are allowed to apply. In this dynamics, the individual quantum trajectories exhibit a measurement-induced entanglement transition from critical to area-law scaling above a critical measurement rate, similar to previously studied models of free fermions under continuous monitoring. Furthermore, we find that the corrective unitary operations can steer the system into a state characterized by charge-density-wave order. Consequently, an additional phase transition occurs, which can be observed at both the level of the quantum trajectory and the quantum channel. We establish that the entanglement transition and the steering transition are fundamentally distinct. The latter transition belongs to the parity-conserving (PC) universality class, arising from the interplay between the inherent fermionic parity and classical labelling. We demonstrate both the entanglement and the steering transitions via efficient numerical simulations of free fermion systems, which confirm the PC universality class of the latter.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"73 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143766731","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

Early Fault-Tolerant Quantum Algorithms in Practice: Application to Ground-State Energy Estimation

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-01 DOI: 10.22331/q-2025-04-01-1682

Oriel Kiss, Utkarsh Azad, Borja Requena, Alessandro Roggero, David Wakeham, Juan Miguel Arrazola

{"title":"Early Fault-Tolerant Quantum Algorithms in Practice: Application to Ground-State Energy Estimation","authors":"Oriel Kiss, Utkarsh Azad, Borja Requena, Alessandro Roggero, David Wakeham, Juan Miguel Arrazola","doi":"10.22331/q-2025-04-01-1682","DOIUrl":"https://doi.org/10.22331/q-2025-04-01-1682","url":null,"abstract":"We investigate the feasibility of early fault-tolerant quantum algorithms focusing on ground-state energy estimation problems. In particular, we examine the computation of the cumulative distribution function (CDF) of the spectral measure of a Hamiltonian and the identification of its discontinuities. Scaling these methods to larger system sizes reveals three key challenges: the smoothness of the CDF for large supports, the lack of tight lower bounds on the overlap with the true ground state, and the difficulty of preparing high-quality initial states. To address these challenges, we propose a signal processing approach to find these estimates automatically, in the regime where the quality of the initial state is unknown. Rather than aiming for exact ground-state energy, we advocate for improving classical estimates by targeting the low-energy support of the initial state. Additionally, we provide quantitative resource estimates, demonstrating a constant factor improvement in the number of samples required to detect a specified change in CDF. Our numerical experiments, conducted on a 26-qubit fully connected Heisenberg model, leverage a truncated density-matrix renormalization group (DMRG) initial state with a low bond dimension. The results show that the predictions from the quantum algorithm align closely with the DMRG-converged energies at larger bond dimensions while requiring several orders of magnitude fewer samples than theoretical estimates suggest. These findings underscore that CDF-based quantum algorithms are a practical and resource-efficient alternative to quantum phase estimation, particularly in resource-constrained scenarios.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"78 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143745686","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

Monte Carlo Simulation of Operator Dynamics and Entanglement in Dual-Unitary Circuits

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-01 DOI: 10.22331/q-2025-04-01-1681

Menghan Song, Zhaoyi Zeng, Ting-Tung Wang, Yi-Zhuang You, Zi Yang Meng, Pengfei Zhang

{"title":"Monte Carlo Simulation of Operator Dynamics and Entanglement in Dual-Unitary Circuits","authors":"Menghan Song, Zhaoyi Zeng, Ting-Tung Wang, Yi-Zhuang You, Zi Yang Meng, Pengfei Zhang","doi":"10.22331/q-2025-04-01-1681","DOIUrl":"https://doi.org/10.22331/q-2025-04-01-1681","url":null,"abstract":"We investigate operator dynamics and entanglement growth in dual-unitary circuits, a class of locally scrambled quantum systems that enables efficient simulation beyond the exponential complexity of the Hilbert space. By mapping the operator evolution to a classical Markov process, we perform Monte Carlo simulations to access the time evolution of local operator density and entanglement with polynomial computational cost. Our results reveal that the operator density converges exponentially to a steady-state value, with analytical bounds that match our simulations. Additionally, we observe a volume-law scaling of operator entanglement across different subregions, and identify a critical transition from maximal to sub-maximal entanglement growth, governed by the circuit’s gate parameter. This transition, confirmed by both mean-field theory and Monte Carlo simulations, provides new insights into operator entanglement dynamics in quantum many-body systems. Our work offers a scalable computational framework for studying long-time operator evolution and entanglement, paving the way for deeper exploration of quantum information dynamics.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"33 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143745685","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

Ring-exchange physics in a chain of three-level ions 三级离子链中的环交换物理学

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-04-01 DOI: 10.22331/q-2025-04-01-1683

Sourav Biswas, E. Rico, Tobias Grass

引用次数: 0

Operational Quantum Reference Frame Transformations

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-03-27 DOI: 10.22331/q-2025-03-27-1680

Titouan Carette, Jan Glowacki, Leon Loveridge

{"title":"Operational Quantum Reference Frame Transformations","authors":"Titouan Carette, Jan Glowacki, Leon Loveridge","doi":"10.22331/q-2025-03-27-1680","DOIUrl":"https://doi.org/10.22331/q-2025-03-27-1680","url":null,"abstract":"Quantum reference frames are needed in quantum theory for much the same reasons that reference frames are in classical theories: to manifest invariance in line with fundamental relativity principles and to provide a basis for the definition of observable quantities. Though around since the 1960s, and used in a wide range of applications, only recently has the means for transforming descriptions between different quantum reference frames been tackled in detail. In this work, we provide a general, operationally motivated framework for quantum reference frames and their transformations, holding for locally compact groups. The work is built around the notion of operational equivalence, in which quantum states that cannot be physically distinguished are identified. For example, we describe the collection of relative observables as a subspace of the algebra of invariants on the composite of system and frame, and from here the set of relative states is constructed through the identification of states which cannot be distinguished by relative observables. Through the notion of framed observables – the formation of joint observables of system and frame – of which the relative observables can be understood as examples, quantum reference frame transformations are then maps between equivalence classes of relative states which respect the framing. We give an explicit realisation in the setting that the initial frame admits a highly localized state with respect to the frame observable. The transformations are invertible exactly when the final frame also has such a localizability property. The procedure we present is in operational agreement with other recent inequivalent constructions on the domain of common applicability, but extends them in a number of ways, and weakens claims of entanglement generation through frame changes.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"29 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143712873","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

On the Computational Hardness of Quantum One-Wayness

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-03-27 DOI: 10.22331/q-2025-03-27-1679

Bruno Cavalar, Eli Goldin, Matthew Gray, Peter Hall, Yanyi Liu, Angelos Pelecanos

{"title":"On the Computational Hardness of Quantum One-Wayness","authors":"Bruno Cavalar, Eli Goldin, Matthew Gray, Peter Hall, Yanyi Liu, Angelos Pelecanos","doi":"10.22331/q-2025-03-27-1679","DOIUrl":"https://doi.org/10.22331/q-2025-03-27-1679","url":null,"abstract":"There is a large body of work studying what forms of computational hardness are needed to realize classical cryptography. In particular, one-way functions and pseudorandom generators can be built from each other, and thus require equivalent computational assumptions to be realized. Furthermore, the existence of either of these primitives implies that $rm{P} neq rm{NP}$, which gives a lower bound on the necessary hardness. One can also define versions of each of these primitives with quantum output: respectively one-way state generators and pseudorandom state generators. Unlike in the classical setting, it is not known whether either primitive can be built from the other. Although it has been shown that pseudorandom state generators for certain parameter regimes can be used to build one-way state generators, the implication has not been previously known in full generality. Furthermore, to the best of our knowledge, the existence of one-way state generators has no known implications in complexity theory. We show that pseudorandom states compressing $n$ bits to $log n + 1$ qubits can be used to build one-way state generators and pseudorandom states compressing $n$ bits to $omega(log n)$ qubits are one-way state generators. This is a nearly optimal result since pseudorandom states with fewer than $c log n$-qubit output can be shown to exist unconditionally. We also show that any one-way state generator can be broken by a quantum algorithm with classical access to a $rm{PP}$ oracle. An interesting implication of our results is that a $t(n)$-copy one-way state generator exists unconditionally, for every $t(n) = o(n/log n)$. This contrasts nicely with the previously known fact that $O(n)$-copy one-way state generators require computational hardness. We also outline a new route towards a black-box separation between one-way state generators and quantum bit commitments.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"12 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143712872","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