PRA: Quantum information

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Recently published articles in Phys. Rev. A in the Table of Content section "Quantum information"
Updated: 32 min 48 sec ago

Digital quantum simulator in the presence of a bath

Fri, 2017-10-20 12:00

Author(s): Yi-Cong Zheng and Hui-Khoon Ng

For a digital quantum simulator (DQS) imitating a target system, we ask the following question: Under what conditions is the simulator dynamics similar to that of the target in the presence of coupling to a bath? In this paper, we derive conditions for close simulation for three different physical r...


[Phys. Rev. A 96, 042329] Published Fri Oct 20, 2017

Categories: Journals, Physics

Detecting metrologically useful asymmetry and entanglement by a few local measurements

Thu, 2017-10-19 12:00

Author(s): Chao Zhang, Benjamin Yadin, Zhi-Bo Hou, Huan Cao, Bi-Heng Liu, Yun-Feng Huang, Reevu Maity, Vlatko Vedral, Chuan-Feng Li, Guang-Can Guo, and Davide Girolami

Important properties of a quantum system are not directly measurable, but they can be disclosed by how fast the system changes under controlled perturbations. In particular, asymmetry and entanglement can be verified by reconstructing the state of a quantum system. Yet, this usually requires experim...


[Phys. Rev. A 96, 042327] Published Thu Oct 19, 2017

Categories: Journals, Physics

Better bounds on optimal measurement and entanglement recovery, with applications to uncertainty and monogamy relations

Thu, 2017-10-19 12:00

Author(s): Joseph M. Renes

We extend the recent bounds of Sason and Verdú relating Rényi entropy and Bayesian hypothesis testing (arXiv:1701.01974.) to the quantum domain and show that they have a number of different applications. First, we obtain a sharper bound relating the optimal probability of correctly distinguishing el...


[Phys. Rev. A 96, 042328] Published Thu Oct 19, 2017

Categories: Journals, Physics

Optimal convex approximations of quantum states

Wed, 2017-10-18 12:00

Author(s): Massimiliano F. Sacchi

We consider the problem of optimally approximating an unavailable quantum state ρ by the convex mixing of states drawn from a set of available states {νi}. The problem is recast to look for the least distinguishable state from ρ among the convex set ∑ipiνi, and the corresponding optimal weights {pi}...


[Phys. Rev. A 96, 042325] Published Wed Oct 18, 2017

Categories: Journals, Physics

Investigating Einstein-Podolsky-Rosen steering of continuous-variable bipartite states by non-Gaussian pseudospin measurements

Wed, 2017-10-18 12:00

Author(s): Yu Xiang, Buqing Xu, Ladislav Mišta, Jr., Tommaso Tufarelli, Qiongyi He, and Gerardo Adesso

Einstein-Podolsky-Rosen (EPR) steering is an asymmetric form of correlations which is intermediate between quantum entanglement and Bell nonlocality, and can be exploited as a resource for quantum communication with one untrusted party. In particular, steering of continuous-variable Gaussian states ...


[Phys. Rev. A 96, 042326] Published Wed Oct 18, 2017

Categories: Journals, Physics

Entanglement-enhanced lidars for simultaneous range and velocity measurements

Mon, 2017-10-16 12:00

Author(s): Quntao Zhuang, Zheshen Zhang, and Jeffrey H. Shapiro

Lidar is a well-known optical technology for measuring a target's range and radial velocity. We describe two lidar systems that use entanglement between transmitted signals and retained idlers to obtain significant quantum enhancements in simultaneous measurements of these parameters. The first enta...


[Phys. Rev. A 96, 040304(R)] Published Mon Oct 16, 2017

Categories: Journals, Physics

Transfer and preservation of entanglement in a hybrid optomechanical system

Mon, 2017-10-16 12:00

Author(s): Qiankun Zhang, Xiangyang Zhang, and Lianzhen Liu

We propose a scheme for entangling a movable mirror and two atomic ensembles in a coupled hybrid optomechanical system. Using the logarithmic negativity for the entanglement measure, we analyze the effect of the coupling strength between the two cavities on the entanglement of the movable mirror and...


[Phys. Rev. A 96, 042320] Published Mon Oct 16, 2017

Categories: Journals, Physics

Tight upper bound for the maximal quantum value of the Svetlichny operators

Mon, 2017-10-16 12:00

Author(s): Ming Li, Shuqian Shen, Naihuan Jing, Shao-Ming Fei, and Xianqing Li-Jost

It is a challenging task to detect genuine multipartite nonlocality (GMNL). In this paper, the problem is considered via computing the maximal quantum value of Svetlichny operators for three-qubit systems and a tight upper bound is obtained. The constraints on the quantum states for the tightness of...


[Phys. Rev. A 96, 042323] Published Mon Oct 16, 2017

Categories: Journals, Physics

Role of coherence during classical and quantum decoherence

Mon, 2017-10-16 12:00

Author(s): Jin-Xing Hou, Si-Yuan Liu, Xiao-Hui Wang, and Wen-Li Yang

The total correlation in a bipartite quantum system is measured by the quantum mutual information I, which consists of quantum discord and classical correlation. However, recent results in quantum information show that coherence, which is a part of total correlation, is more general and more fundame...


[Phys. Rev. A 96, 042324] Published Mon Oct 16, 2017

Categories: Journals, Physics

Verifying bound entanglement of dephased Werner states

Mon, 2017-10-16 12:00

Author(s): P. Thomas, M. Bohmann, and W. Vogel

The verification of quantum entanglement under the influence of realistic noise and decoherence is crucial for the development of quantum technologies. Unfortunately, a full entanglement characterization is generally not possible with most entanglement criteria such as entanglement witnesses or the ...


[Phys. Rev. A 96, 042321] Published Mon Oct 16, 2017

Categories: Journals, Physics

Experimental demonstration of perturbative anticrossing mitigation using nonuniform driver Hamiltonians

Mon, 2017-10-16 12:00

Author(s): Trevor Lanting, Andrew D. King, Bram Evert, and Emile Hoskinson

Perturbative anticrossings have long been identified as a potential computational bottleneck for quantum annealing. This bottleneck can appear, for example, when a uniform transverse driver Hamiltonian is applied to each qubit. Previous theoretical research sought to alleviate such anticrossings by ...


[Phys. Rev. A 96, 042322] Published Mon Oct 16, 2017

Categories: Journals, Physics

Thermal effects on coherence and excitation transfer

Fri, 2017-10-13 12:00

Author(s): Laleh Memarzadeh and Azam Mani

To control and utilize quantum features in small scale for practical applications such as quantum transport, it is crucial to gain a deep understanding of the quantum characteristics of states such as coherence. Here by introducing a technique that simplifies solving the dynamical equation, we study...


[Phys. Rev. A 96, 042318] Published Fri Oct 13, 2017

Categories: Journals, Physics

Estimation of gradients in quantum metrology

Fri, 2017-10-13 12:00

Author(s): Sanah Altenburg, Michał Oszmaniec, Sabine Wölk, and Otfried Gühne

We develop a general theory to estimate magnetic field gradients in quantum metrology. We consider a system of N particles distributed on a line whose internal degrees of freedom interact with a magnetic field. Usually gradient estimation is based on precise measurements of the magnetic field at two...


[Phys. Rev. A 96, 042319] Published Fri Oct 13, 2017

Categories: Journals, Physics

Resonator reset in circuit QED by optimal control for large open quantum systems

Thu, 2017-10-12 12:00

Author(s): Samuel Boutin, Christian Kraglund Andersen, Jayameenakshi Venkatraman, Andrew J. Ferris, and Alexandre Blais

We study an implementation of the open GRAPE (gradient ascent pulse engineering) algorithm well suited for large open quantum systems. While typical implementations of optimal control algorithms for open quantum systems rely on explicit matrix exponential calculations, our implementation avoids thes...


[Phys. Rev. A 96, 042315] Published Thu Oct 12, 2017

Categories: Journals, Physics

Fault-tolerance thresholds for the surface code with fabrication errors

Thu, 2017-10-12 12:00

Author(s): James M. Auger, Hussain Anwar, Mercedes Gimeno-Segovia, Thomas M. Stace, and Dan E. Browne

The construction of topological error correction codes requires the ability to fabricate a lattice of physical qubits embedded on a manifold with a nontrivial topology such that the quantum information is encoded in the global degrees of freedom (i.e., the topology) of the manifold. However, the man...


[Phys. Rev. A 96, 042316] Published Thu Oct 12, 2017

Categories: Journals, Physics

Quantum gate description for induced coherence without induced emission and its applications

Thu, 2017-10-12 12:00

Author(s): Sahar Alipour, Mario Krenn, and Anton Zeilinger

We introduce unitary quantum gates for photon pair creation in spontaneous parametric down-conversion nonlinear crystals (NLs) and for photon path alignment. These are the two key ingredients for the method of induced coherence without induced emission and many ensuing variations thereof. The diffic...


[Phys. Rev. A 96, 042317] Published Thu Oct 12, 2017

Categories: Journals, Physics

Optimally cloned binary coherent states

Wed, 2017-10-11 12:00

Author(s): C. R. Müller, G. Leuchs, Ch. Marquardt, and U. L. Andersen

Binary coherent state alphabets can be represented in a two-dimensional Hilbert space. We capitalize this formal connection between the otherwise distinct domains of qubits and continuous variable states to map binary phase-shift keyed coherent states onto the Bloch sphere and to derive their quantu...


[Phys. Rev. A 96, 042311] Published Wed Oct 11, 2017

Categories: Journals, Physics

Imperfect state preparation in continuous-variable quantum key distribution

Wed, 2017-10-11 12:00

Author(s): Wenyuan Liu, Xuyang Wang, Ning Wang, Shanna Du, and Yongmin Li

In continuous-variable quantum key distribution, the loss and excess noise of the quantum channel are key parameters that determine the secure key rate and the maximal distribution distance. We investigate the imperfect quantum state preparation in Gaussian modulation coherent-state protocol both th...


[Phys. Rev. A 96, 042312] Published Wed Oct 11, 2017

Categories: Journals, Physics

Necessary condition for local distinguishability of maximally entangled states: Beyond orthogonality preservation

Wed, 2017-10-11 12:00

Author(s): Tanmay Singal, Ramij Rahaman, Sibasish Ghosh, and Guruprasad Kar

The (im)possibility of local distinguishability of orthogonal multipartite quantum states still remains an intriguing question. Beyond C3⊗C3, the problem remains unsolved even for maximally entangled states (MESs). So far, the only known condition for the local distinguishability of states is the we...


[Phys. Rev. A 96, 042314] Published Wed Oct 11, 2017

Categories: Journals, Physics

Quantum annealing with a nonvanishing final value of the transverse field

Tue, 2017-10-10 12:00

Author(s): Kohji Nishimura and Hidetoshi Nishimori

We study the problem to infer the original ground state of a spin-glass Hamiltonian out of the information from the Hamiltonian with interactions deviated from the original ones. Our motivation comes from quantum annealing on a real device in which the values of interactions are degraded by noise. W...


[Phys. Rev. A 96, 042310] Published Tue Oct 10, 2017

Categories: Journals, Physics