We consider a class of games between two competing players that take turns acting on the same many-body quantum register. Each player can perform unitary operations on the register, and after each one of them acts on the register the energy is measured. Player A aims to maximize the energy while player B to minimize it. This class of zero-sum games has a clear second mover advantage if both players can entangle the same portion of the register. We show, however, that if the first player can entangle a larger number of qubits than the second player (which we refer to as having quantum edge), then the second mover advantage can be significantly reduced. We study the game for different types of quantum edge of player A versus player B and for different sizes of the register, in particular, scenarios in which absolutely maximally entangled states cannot be achieved. In this case, we also study the effectiveness of using random unitaries. Last, we consider mixed initial preparations of the register, in which case the player with a quantum edge can rely on strategies stemming from the theory of ergotropy of quantum batteries.
我们考虑的是两个竞争者轮流作用于同一个多体量子寄存器的一类游戏。每个玩家都可以对寄存器进行单元操作，在每个玩家对寄存器进行操作后，都要测量能量。玩家 A 的目标是最大化能量，而玩家 B 则是最小化能量。如果双方都能纠缠寄存器的相同部分，那么这类零和博弈具有明显的后发优势。不过，我们的研究表明，如果第一名玩家能比第二名玩家纠缠更多的量子比特（我们称之为量子优势），那么第二名玩家的优势就会大大降低。我们研究了棋手 A 与棋手 B 不同类型的量子优势和不同大小的寄存器的博弈，特别是无法实现绝对最大纠缠状态的情况。在这种情况下，我们还研究了使用随机单元的有效性。最后，我们考虑了注册表的混合初始准备情况，在这种情况下，拥有量子边的棋手可以依赖量子电池各向异性理论的策略。
{"title":"Entangling capabilities and unitary quantum games","authors":"Rebecca Erbanni, Antonios Varvitsiotis, Dario Poletti","doi":"10.1103/physreva.110.022413","DOIUrl":"https://doi.org/10.1103/physreva.110.022413","url":null,"abstract":"We consider a class of games between two competing players that take turns acting on the same many-body quantum register. Each player can perform unitary operations on the register, and after each one of them acts on the register the energy is measured. Player A aims to maximize the energy while player B to minimize it. This class of zero-sum games has a clear second mover advantage if both players can entangle the same portion of the register. We show, however, that if the first player can entangle a larger number of qubits than the second player (which we refer to as having quantum edge), then the second mover advantage can be significantly reduced. We study the game for different types of quantum edge of player A versus player B and for different sizes of the register, in particular, scenarios in which absolutely maximally entangled states cannot be achieved. In this case, we also study the effectiveness of using random unitaries. Last, we consider mixed initial preparations of the register, in which case the player with a quantum edge can rely on strategies stemming from the theory of ergotropy of quantum batteries.","PeriodicalId":20146,"journal":{"name":"Physical Review A","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141943312","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 : 2024-08-07DOI: 10.1103/physreva.110.022410
Jan Lennart Bönsel, Satoya Imai, Ye-Chao Liu, Otfried Gühne
How can we analyze quantum correlations in large and noisy systems without quantum state tomography? An established method is to measure total angular momenta and employ the so-called spin-squeezing inequalities based on their expectations and variances. This allows detection of metrologically useful entanglement, but efficient strategies for estimating such nonlinear quantities have yet to be determined. In this paper we show that spin-squeezing inequalities can not only be evaluated by measurements of the total angular momentum but also by two-qubit correlations, either involving all pair correlations or randomly chosen pair correlations. Then we analyze the estimation errors of our approaches in terms of a hypothesis test. For this purpose, we discuss how error bounds can be derived for nonlinear estimators with the help of their variances, characterizing the probability of falsely detecting a separable state as entangled. We focus on the spin-squeezing inequalities in multiqubit systems. Our methods, however, can also be applied to spin-squeezing inequalities for qudits or for the statistical treatment of other nonlinear parameters of quantum states.
{"title":"Error estimation of different schemes to measure spin-squeezing inequalities","authors":"Jan Lennart Bönsel, Satoya Imai, Ye-Chao Liu, Otfried Gühne","doi":"10.1103/physreva.110.022410","DOIUrl":"https://doi.org/10.1103/physreva.110.022410","url":null,"abstract":"How can we analyze quantum correlations in large and noisy systems without quantum state tomography? An established method is to measure total angular momenta and employ the so-called spin-squeezing inequalities based on their expectations and variances. This allows detection of metrologically useful entanglement, but efficient strategies for estimating such nonlinear quantities have yet to be determined. In this paper we show that spin-squeezing inequalities can not only be evaluated by measurements of the total angular momentum but also by two-qubit correlations, either involving all pair correlations or randomly chosen pair correlations. Then we analyze the estimation errors of our approaches in terms of a hypothesis test. For this purpose, we discuss how error bounds can be derived for nonlinear estimators with the help of their variances, characterizing the probability of falsely detecting a separable state as entangled. We focus on the spin-squeezing inequalities in multiqubit systems. Our methods, however, can also be applied to spin-squeezing inequalities for qudits or for the statistical treatment of other nonlinear parameters of quantum states.","PeriodicalId":20146,"journal":{"name":"Physical Review A","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141943417","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 : 2024-08-07DOI: 10.1103/physreva.110.022606
Ben Reggio, Nouman Butt, Andrew Lytle, Patrick Draper
The Pauli strings appearing in the decomposition of an operator can be can be grouped into commuting families, reducing the number of quantum circuits needed to measure the expectation value of the operator. We detail an algorithm to completely partition the full set of Pauli strings acting on any number of qubits into the minimal number of sets of commuting families, and we provide python code to perform the partitioning. The partitioning method scales linearly with the size of the set of Pauli strings and it naturally provides a fast method of diagonalizing the commuting families with quantum gates. We provide a package that integrates the partitioning into qiskit, and use this to benchmark the algorithm with dense Hamiltonians, such as those that arise in matrix quantum mechanics models, on IBM hardware. We demonstrate computational speedups close to the theoretical limit of relative to qubit-wise commuting groupings, for qubits.
在算子分解中出现的保利弦可以被归类为换向族，从而减少测量算子期望值所需的量子电路数量。我们详细介绍了将作用于任意数量量子比特的全套保利弦完全划分为最小数量换向族集合的算法，并提供了执行划分的 python 代码。分割方法与保利弦集的大小成线性比例，它自然提供了一种用量子门对角化换向族的快速方法。我们提供了一个软件包，将分割方法集成到 qiskit 中，并利用它在 IBM 硬件上对密集哈密顿（如矩阵量子力学模型中出现的哈密顿）进行基准测试。我们展示了在 m=2,...6 量子位时，相对于量子位换向分组，计算速度接近理论极限 (3/2)m。
{"title":"Fast partitioning of Pauli strings into commuting families for optimal expectation value measurements of dense operators","authors":"Ben Reggio, Nouman Butt, Andrew Lytle, Patrick Draper","doi":"10.1103/physreva.110.022606","DOIUrl":"https://doi.org/10.1103/physreva.110.022606","url":null,"abstract":"The Pauli strings appearing in the decomposition of an operator can be can be grouped into commuting families, reducing the number of quantum circuits needed to measure the expectation value of the operator. We detail an algorithm to completely partition the full set of Pauli strings acting on any number of qubits into the minimal number of sets of commuting families, and we provide python code to perform the partitioning. The partitioning method scales linearly with the size of the set of Pauli strings and it naturally provides a fast method of diagonalizing the commuting families with quantum gates. We provide a package that integrates the partitioning into <span>qiskit</span>, and use this to benchmark the algorithm with dense Hamiltonians, such as those that arise in matrix quantum mechanics models, on IBM hardware. We demonstrate computational speedups close to the theoretical limit of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mrow><mo>(</mo><mn>3</mn><mo>/</mo><mn>2</mn><mo>)</mo></mrow><mi>m</mi></msup></math> relative to qubit-wise commuting groupings, for <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>m</mi><mo>=</mo><mn>2</mn><mo>,</mo><mo>...</mo><mspace width=\"0.16em\"></mspace><mo>,</mo><mn>6</mn></mrow></math> qubits.","PeriodicalId":20146,"journal":{"name":"Physical Review A","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141943414","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 : 2024-08-07DOI: 10.1103/physreva.110.023711
Yan-Zi Jing, Ke-Wen Xiao, Wen-Yuan Wang
The investigation of pseudo-Hermitian systems has garnered widespread attention due to their distinctive property of purely real eigenvalues splitting into complex conjugate pairs. This transition profoundly modifies the system's behavior, specifically giving rise to remarkable dynamical effects. Here we explore the novel characteristics of phase transitions and dynamic currents in a pseudo-Hermitian system of coupled sites with tunable gain and loss. With tunable gain and loss, we verify that the system uniquely supports two pseudo-Hermitian configurations, which exhibit distinct symmetries. The phase transitions from the -symmetric phase to the spontaneous broken -symmetric phase, along with the associated high-order exceptional points (EPs), are unambiguously demonstrated in both types of symmetry configurations. We measure the dynamic current within the four coupled sites, which allows us to probe the EPs and phase transitions between distinct phases. Our results offer insights into the phase transitions and dynamics of pseudo-Hermitian systems, with potential applications in the design and manipulation of novel quantum phenomena across various fields including photonics and other related quantum systems.
由于伪赫米提系统具有纯实特征值分裂成复数共轭对的独特性质，对该系统的研究受到了广泛关注。这种转变深刻地改变了系统的行为，特别是产生了显著的动力学效应。在这里，我们探讨了具有可调增益和损耗的耦合位点的伪赫米提系统中相变和动态电流的新特性。在增益和损耗可调的情况下，我们验证了该系统唯一支持两种伪赫米提构型，这两种构型表现出截然不同的对称性。从 PT 对称相到自发破坏的 PT 对称相的相变，以及相关的高阶异常点 (EP)，在这两种对称配置中都得到了明确的证明。我们测量了四个耦合位点内的动态电流，这使我们能够探测 EP 和不同相位之间的相变。我们的研究结果提供了对伪赫米提系统相变和动力学的见解，有望应用于设计和操纵包括光子学和其他相关量子系统在内的各个领域的新型量子现象。
{"title":"Phase transitions and dynamic currents in a pseudo-Hermitian system of coupled sites with tunable gain and loss","authors":"Yan-Zi Jing, Ke-Wen Xiao, Wen-Yuan Wang","doi":"10.1103/physreva.110.023711","DOIUrl":"https://doi.org/10.1103/physreva.110.023711","url":null,"abstract":"The investigation of pseudo-Hermitian systems has garnered widespread attention due to their distinctive property of purely real eigenvalues splitting into complex conjugate pairs. This transition profoundly modifies the system's behavior, specifically giving rise to remarkable dynamical effects. Here we explore the novel characteristics of phase transitions and dynamic currents in a pseudo-Hermitian system of coupled sites with tunable gain and loss. With tunable gain and loss, we verify that the system uniquely supports two pseudo-Hermitian configurations, which exhibit distinct symmetries. The phase transitions from the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi mathvariant=\"script\">PT</mi></math>-symmetric phase to the spontaneous broken <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi mathvariant=\"script\">PT</mi></math>-symmetric phase, along with the associated high-order exceptional points (EPs), are unambiguously demonstrated in both types of symmetry configurations. We measure the dynamic current within the four coupled sites, which allows us to probe the EPs and phase transitions between distinct phases. Our results offer insights into the phase transitions and dynamics of pseudo-Hermitian systems, with potential applications in the design and manipulation of novel quantum phenomena across various fields including photonics and other related quantum systems.","PeriodicalId":20146,"journal":{"name":"Physical Review A","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141943419","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 : 2024-08-07DOI: 10.1103/physreva.110.022211
Gergely Bunth, József Pitrik, Tamás Titkos, Dániel Virosztek
Quantum Wasserstein divergences are modified versions of quantum Wasserstein distances defined by channels and they have been conjectured to be genuine metrics on quantum state spaces by De Palma and Trevisan. We prove triangle inequality for quantum Wasserstein divergences for every quantum system described by a separable Hilbert space and any quadratic cost operator under the assumption that a particular state involved is pure and all the states have finite energy. We also provide strong numerical evidence suggesting that the triangle inequality holds in general for an arbitrary choice of states.
{"title":"Metric property of quantum Wasserstein divergences","authors":"Gergely Bunth, József Pitrik, Tamás Titkos, Dániel Virosztek","doi":"10.1103/physreva.110.022211","DOIUrl":"https://doi.org/10.1103/physreva.110.022211","url":null,"abstract":"Quantum Wasserstein divergences are modified versions of quantum Wasserstein distances defined by channels and they have been conjectured to be genuine metrics on quantum state spaces by De Palma and Trevisan. We prove triangle inequality for quantum Wasserstein divergences for every quantum system described by a separable Hilbert space and any quadratic cost operator under the assumption that a particular state involved is pure and all the states have finite energy. We also provide strong numerical evidence suggesting that the triangle inequality holds in general for an arbitrary choice of states.","PeriodicalId":20146,"journal":{"name":"Physical Review A","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141943418","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 : 2024-08-07DOI: 10.1103/physreva.110.023509
Souvik Mondal, Murilo S. Baptista, Kapil Debnath
Optomechanical systems produce chaotic behavior due to the nonlinear interaction between photons and phonons, and the same systems are used to understand the synthetic fields as well. Here, we report on the study of chaotic behavior in the presence of a phononic synthetic magnetic field in a closed-loop configuration consisting of a single optical mode and two mechanical modes. The modulation phase of the mechanical coupling between the two mechanical modes plays a critical role in determining the mechanical and optical intensity dynamics in the nonlinear regime. Our study shows the dark mode breaking effect in the presence of a synthetic magnetic field, which brings about a complex way of mechanical energy exchange that causes the cavity field to alternate between chaotic and regular behavior periodically in the temporal domain. However, in the stronger nonlinear regime the temporal dynamics demonstrate predominantly chaotic behavior. With the advent of advanced fabrication technologies, this study holds promises in developing phase tunable integrated low-power chaotic light sources to support efficient optical secure communication systems.
{"title":"Chaotic dynamics under the influence of a synthetic magnetic field in an optomechanical system","authors":"Souvik Mondal, Murilo S. Baptista, Kapil Debnath","doi":"10.1103/physreva.110.023509","DOIUrl":"https://doi.org/10.1103/physreva.110.023509","url":null,"abstract":"Optomechanical systems produce chaotic behavior due to the nonlinear interaction between photons and phonons, and the same systems are used to understand the synthetic fields as well. Here, we report on the study of chaotic behavior in the presence of a phononic synthetic magnetic field in a closed-loop configuration consisting of a single optical mode and two mechanical modes. The modulation phase of the mechanical coupling between the two mechanical modes plays a critical role in determining the mechanical and optical intensity dynamics in the nonlinear regime. Our study shows the dark mode breaking effect in the presence of a synthetic magnetic field, which brings about a complex way of mechanical energy exchange that causes the cavity field to alternate between chaotic and regular behavior periodically in the temporal domain. However, in the stronger nonlinear regime the temporal dynamics demonstrate predominantly chaotic behavior. With the advent of advanced fabrication technologies, this study holds promises in developing phase tunable integrated low-power chaotic light sources to support efficient optical secure communication systems.","PeriodicalId":20146,"journal":{"name":"Physical Review A","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141943326","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 : 2024-08-07DOI: 10.1103/physreva.110.l020802
Egor Trushin, Jannis Erhard, Andreas Görling
Electronic structure methods based on the Kohn-Sham (KS) formalism of density-functional theory are ubiquitously and highly successfully used in physics, chemistry, and materials science. Whether the KS formalism is universally applicable is, however, an open question because it is not known whether a KS model system exists for all physical electron systems. This is the question of whether electron densities of real physical systems are always noninteracting -representable. Here we give indications that this is not always the case. To that end, we calculated highly accurate electron densities of first and second row atoms with a partially filled shell by high-level quantum chemistry methods and by full configuration interaction and then tried to determine the effective KS potential by KS inversion. Except for nitrogen and phosphorus this was only possible for an occupation pattern violating the Aufbau principle. This means that the resulting wave function is not a ground state of the KS Hamiltonian operator and therefore not a valid KS wave function, which indicates that the KS formalism is not always applicable. Strategies to avoid the presented -representability problem are discussed.
{"title":"Violations of the v-representability condition underlying Kohn-Sham density-functional theory","authors":"Egor Trushin, Jannis Erhard, Andreas Görling","doi":"10.1103/physreva.110.l020802","DOIUrl":"https://doi.org/10.1103/physreva.110.l020802","url":null,"abstract":"Electronic structure methods based on the Kohn-Sham (KS) formalism of density-functional theory are ubiquitously and highly successfully used in physics, chemistry, and materials science. Whether the KS formalism is universally applicable is, however, an open question because it is not known whether a KS model system exists for all physical electron systems. This is the question of whether electron densities of real physical systems are always noninteracting <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>v</mi></math>-representable. Here we give indications that this is not always the case. To that end, we calculated highly accurate electron densities of first and second row atoms with a partially filled <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>p</mi></math> shell by high-level quantum chemistry methods and by full configuration interaction and then tried to determine the effective KS potential by KS inversion. Except for nitrogen and phosphorus this was only possible for an occupation pattern violating the Aufbau principle. This means that the resulting wave function is not a ground state of the KS Hamiltonian operator and therefore not a valid KS wave function, which indicates that the KS formalism is not always applicable. Strategies to avoid the presented <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>v</mi></math>-representability problem are discussed.","PeriodicalId":20146,"journal":{"name":"Physical Review A","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141943415","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 : 2024-08-06DOI: 10.1103/physreva.110.022408
Chellasamy Jebarathinam, Gautam Sharma, Sk Sazim, Remigiusz Augusiak
Self-testing of quantum devices based on observed measurement statistics is a method to certify quantum systems using minimal resources. In Irfan et al. [A. A. M. Irfan, K. Mayer, G. Ortiz, and E. Knill, Phys. Rev. A101, 032106 (2020)] a scheme based on observing measurement statistics that demonstrate Kochen-Specker contextuality has been shown to certify two-qubit entangled states and measurements without the requirement of spatial separation between the subsystems. However, this scheme assumes a set of compatibility conditions on the measurements which are crucial to demonstrating Kochen-Specker contextuality. In this paper, we propose a self-testing protocol to certify the above two-qubit states and measurements without the assumption of the compatibility conditions, and at the same time without requiring the spatial separation between the subsystems. Our protocol is based on the observation of sequential correlations leading to the maximal violation of a temporal inequality derived from noncontextuality inequality. Moreover, our protocol is robust to small experimental errors or noise.
基于观测到的测量统计数据对量子设备进行自测试，是一种利用最少资源对量子系统进行认证的方法。在伊尔凡等人 [A. A. M. Irfan, K. Mayer, G. Ortiz, and E. Knill.A.M.Irfan、K.Mayer、G.Ortiz 和 E.Knill，Phys. Rev. A 101, 032106 (2020)]中展示了一种基于观测证明 Kochen-Specker 上下文性的测量统计量的方案，它可以认证双量子比特纠缠状态和测量，而不需要子系统之间的空间分离。然而，这一方案假设了一组测量的兼容性条件，而这些条件对于证明 Kochen-Specker 上下文相关性至关重要。在本文中，我们提出了一种自测试协议，在不假定兼容性条件的情况下认证上述双量子比特状态和测量，同时也不要求子系统之间的空间分离。我们的协议基于对顺序相关性的观测，这种观测会导致对非上下文不等式衍生出的时间不等式的最大违反。此外，我们的协议对微小的实验误差或噪音也具有鲁棒性。
{"title":"Certification of two-qubit quantum systems with temporal inequality","authors":"Chellasamy Jebarathinam, Gautam Sharma, Sk Sazim, Remigiusz Augusiak","doi":"10.1103/physreva.110.022408","DOIUrl":"https://doi.org/10.1103/physreva.110.022408","url":null,"abstract":"Self-testing of quantum devices based on observed measurement statistics is a method to certify quantum systems using minimal resources. In Irfan <i>et al.</i> [A. A. M. Irfan, K. Mayer, G. Ortiz, and E. Knill, <span>Phys. Rev. A</span> <b>101</b>, 032106 (2020)] a scheme based on observing measurement statistics that demonstrate Kochen-Specker contextuality has been shown to certify two-qubit entangled states and measurements without the requirement of spatial separation between the subsystems. However, this scheme assumes a set of compatibility conditions on the measurements which are crucial to demonstrating Kochen-Specker contextuality. In this paper, we propose a self-testing protocol to certify the above two-qubit states and measurements without the assumption of the compatibility conditions, and at the same time without requiring the spatial separation between the subsystems. Our protocol is based on the observation of sequential correlations leading to the maximal violation of a temporal inequality derived from noncontextuality inequality. Moreover, our protocol is robust to small experimental errors or noise.","PeriodicalId":20146,"journal":{"name":"Physical Review A","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141943317","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 : 2024-08-06DOI: 10.1103/physreva.110.023306
Aitor Alaña, Michele Modugno, Pablo Capuzzi, D. M. Jezek
We analyze the pinning of vortices for a stationary rotating dipolar supersolid along the low-density paths between droplets as a function of the rotation frequency. We restrict ourselves to the stationary configurations of vortices with the same symmetry as that of the array of droplets. In particular, such an analysis clearly reveals that vortices are not only pinned at local density minima, but instead their coordinates are smooth functions of the rotation frequency. Our approach to explaining such a behavior exploits the fact that the wave function of each rotating droplet acquires a linear phase on the coordinates. Hence, the relative phases between the nearest neighboring droplets allow us to predict the position of the vortices in the intermediate low-density region. Here, we show that, for a droplet distribution forming a triangular lattice, the phases of three neighboring droplets are needed for the correct description of the vortex location. In particular, for our confined system, we demonstrate that the estimate accurately reproduces the extended Gross-Pitaevskii results in the spatial regions where the neighboring droplets are well defined.
{"title":"Phase-induced vortex pinning in rotating supersolid dipolar systems","authors":"Aitor Alaña, Michele Modugno, Pablo Capuzzi, D. M. Jezek","doi":"10.1103/physreva.110.023306","DOIUrl":"https://doi.org/10.1103/physreva.110.023306","url":null,"abstract":"We analyze the pinning of vortices for a stationary rotating dipolar supersolid along the low-density paths between droplets as a function of the rotation frequency. We restrict ourselves to the stationary configurations of vortices with the same symmetry as that of the array of droplets. In particular, such an analysis clearly reveals that vortices are not only pinned at local density minima, but instead their coordinates are smooth functions of the rotation frequency. Our approach to explaining such a behavior exploits the fact that the wave function of each rotating droplet acquires a linear phase on the coordinates. Hence, the relative phases between the nearest neighboring droplets allow us to predict the position of the vortices in the intermediate low-density region. Here, we show that, for a droplet distribution forming a triangular lattice, the phases of three neighboring droplets are needed for the correct description of the vortex location. In particular, for our confined system, we demonstrate that the estimate accurately reproduces the extended Gross-Pitaevskii results in the spatial regions where the neighboring droplets are well defined.","PeriodicalId":20146,"journal":{"name":"Physical Review A","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141943315","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 : 2024-08-06DOI: 10.1103/physreva.110.022605
Di Luo, Xin Liu, Kaibiao Qin, Zhenrong Zhang, Kejin Wei
The advantage distillation (AD) method has proven effective in improving the performance of quantum key distribution (QKD). In this paper we introduce the AD method into a recently proposed asynchronous measurement-device-independent (AMDI) QKD protocol, taking finite-key effects into account. Simulation results show that the AD method significantly enhances AMDI QKD, e.g., extending the transmission distance by 16 km with a total pulse count of , and enables AMDI QKD, previously unable to generate keys, to generate keys with a misalignment error rate of . As the AD method can be directly integrated into the current system through refined postprocessing, our results facilitate the practical implementation of AMDI QKD in various applications, particularly in scenarios with high channel losses and misalignment errors.
{"title":"Practical asynchronous measurement-device-independent quantum key distribution with advantage distillation","authors":"Di Luo, Xin Liu, Kaibiao Qin, Zhenrong Zhang, Kejin Wei","doi":"10.1103/physreva.110.022605","DOIUrl":"https://doi.org/10.1103/physreva.110.022605","url":null,"abstract":"The advantage distillation (AD) method has proven effective in improving the performance of quantum key distribution (QKD). In this paper we introduce the AD method into a recently proposed asynchronous measurement-device-independent (AMDI) QKD protocol, taking finite-key effects into account. Simulation results show that the AD method significantly enhances AMDI QKD, e.g., extending the transmission distance by 16 km with a total pulse count of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>N</mi><mo>=</mo><mn>7.24</mn><mo>×</mo><msup><mn>10</mn><mn>13</mn></msup></mrow></math>, and enables AMDI QKD, previously unable to generate keys, to generate keys with a misalignment error rate of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>10</mn><mo>%</mo></mrow></math>. As the AD method can be directly integrated into the current system through refined postprocessing, our results facilitate the practical implementation of AMDI QKD in various applications, particularly in scenarios with high channel losses and misalignment errors.","PeriodicalId":20146,"journal":{"name":"Physical Review A","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141943323","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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