PRA: Quantum information

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Recently published articles in Phys. Rev. A in the Table of Content section "Quantum information"
Updated: 26 min 51 sec ago

Reverse quantum annealing of the $p$-spin model with relaxation

Tue, 2020-02-25 11:00

Author(s): Gianluca Passarelli, Ka-Wa Yip, Daniel A. Lidar, Hidetoshi Nishimori, and Procolo Lucignano

In reverse quantum annealing, the initial state is an eigenstate of the final problem Hamiltonian and the transverse field is cycled rather than strictly decreased as in standard (forward) quantum annealing. We present a numerical study of the reverse quantum annealing protocol applied to the p-spin...

[Phys. Rev. A 101, 022331] Published Tue Feb 25, 2020

Categories: Journals, Physics

Short-depth circuits for efficient expectation-value estimation

Mon, 2020-02-24 11:00

Author(s): A. Roggero and A. Baroni

The evaluation of expectation values TrρO for some pure state ρ and Hermitian operator O is of central importance in a variety of quantum algorithms. Near-optimal techniques have been developed in the past and require a number of measurements N approaching the Heisenberg limit N=O1/ε as a function o...

[Phys. Rev. A 101, 022328] Published Mon Feb 24, 2020

Categories: Journals, Physics

Entanglement generation via power-of-<span class="sc">swap</span> operations between dynamic electron-spin qubits

Mon, 2020-02-24 11:00

Author(s): Hugo V. Lepage, Aleksander A. Lasek, David R. M. Arvidsson-Shukur, and Crispin H. W. Barnes

Surface acoustic waves (SAWs) can create moving quantum dots in piezoelectric materials. Here we show how electron-spin qubits located on dynamic quantum dots can be entangled. Previous theoretical and numerical models of quantum-dot entanglement generation have been insufficient to study quantum dy...

[Phys. Rev. A 101, 022329] Published Mon Feb 24, 2020

Categories: Journals, Physics

Noncyclic geometric quantum computation with shortcut to adiabaticity

Mon, 2020-02-24 11:00

Author(s): Qing-Xian Lv, Zhen-Tao Liang, Hong-Zhi Liu, Jia-Hao Liang, Kai-Yu Liao, and Yan-Xiong Du

Fast and robust quantum gates are the cornerstones of fault-tolerance quantum computation. In this paper, as opposed to the previous proposals which use cyclic geometric phases, we propose to realize quantum computation based on noncyclic geometric evolution. The superiority of the noncyclic scheme ...

[Phys. Rev. A 101, 022330] Published Mon Feb 24, 2020

Categories: Journals, Physics

Persistent spin squeezing of a dissipative one-axis twisting model embedded in a general thermal environment

Fri, 2020-02-21 11:00

Author(s): Yong-Hong Ma, Quan-Zhen Ding, and Ting Yu

We investigate spin squeezing for a one-axis twisting (OAT) model coupled to a general non-Markovian environment in a finite-temperature regime. Using the non-Markovian quantum state diffusion and master equation approach, we numerically study non-Markovian spin-squeezing generation in the OAT model...

[Phys. Rev. A 101, 022327] Published Fri Feb 21, 2020

Categories: Journals, Physics

Characterization of exact one-query quantum algorithms

Thu, 2020-02-20 11:00

Author(s): Weijiang Chen, Zekun Ye, and Lvzhou Li

The quantum query model is one of the most important models in quantum computing. Several well-known quantum algorithms are captured by this model, including the Deutsch-Jozsa algorithm, the Simon algorithm, the Grover algorithm, and others. In this paper, we characterize the computational power of ...

[Phys. Rev. A 101, 022325] Published Thu Feb 20, 2020

Categories: Journals, Physics

Necessary conditions for steerability of two qubits from consideration of local operations

Thu, 2020-02-20 11:00

Author(s): Travis J. Baker and Howard M. Wiseman

Einstein-Podolsky-Rosen (EPR) steering refers to the ability of one observer to convince a distant observer that they share entanglement by making local measurements. Determining which states allow a demonstration of EPR steering remains an open problem in general. Here, we outline and demonstrate a...

[Phys. Rev. A 101, 022326] Published Thu Feb 20, 2020

Categories: Journals, Physics

Row and column iteration methods to solve linear systems on a quantum computer

Wed, 2020-02-19 11:00

Author(s): Changpeng Shao and Hua Xiang

We consider the quantum implementations of two classical iterative solvers for a system of linear equations, including the row (Kaczmarz) method which utilizes a row of the coefficient matrix in each iteration step, and the column (coordinate descent) method which uses a column instead. These two me...

[Phys. Rev. A 101, 022322] Published Wed Feb 19, 2020

Categories: Journals, Physics

Subwavelength quantum imaging with noisy detectors

Wed, 2020-02-19 11:00

Author(s): Cosmo Lupo

It has been recently shown that an interferometric measurement may allow for subwavelength resolution of incoherent light. Whereas this holds for noiseless detectors, one could expect that the resolution is in practice limited by the signal-to-noise ratio. Here I present a qualitative assessment of ...

[Phys. Rev. A 101, 022323] Published Wed Feb 19, 2020

Categories: Journals, Physics

Experimental certification of the steering criterion based on a general entropic uncertainty relation

Wed, 2020-02-19 11:00

Author(s): Huan Yang, Zhi-Yong Ding, Dong Wang, Hao Yuan, Xue-Ke Song, Jie Yang, Chang-Jin Zhang, and Liu Ye

Quantum steering describes a phenomenon whereby one system can immediately influence another via local measurements. It can be detected by violating the powerful and useful steering criterion based on a general entropic uncertainty relation. This criterion can be straightforwardly evaluated by using...

[Phys. Rev. A 101, 022324] Published Wed Feb 19, 2020

Categories: Journals, Physics

Experimental realization of self-guided quantum process tomography

Tue, 2020-02-18 11:00

Author(s): Zhibo Hou, Jun-Feng Tang, Christopher Ferrie, Guo-Yong Xiang, Chuan-Feng Li, and Guang-Can Guo

Characterization of quantum processes is a preliminary step necessary in the development of quantum technology. The conventional method uses standard quantum process tomography, which requires d2 input states and d4 quantum measurements for a d-dimensional Hilbert space. These experimental requireme...

[Phys. Rev. A 101, 022317] Published Tue Feb 18, 2020

Categories: Journals, Physics

Continuous phase-space representations for finite-dimensional quantum states and their tomography

Tue, 2020-02-18 11:00

Author(s): Bálint Koczor, Robert Zeier, and Steffen J. Glaser

Continuous phase spaces have become a powerful tool for describing, analyzing, and tomographically reconstructing quantum states in quantum optics and beyond. A plethora of these phase-space techniques are known, however a thorough understanding of their relations is still lacking for finite-dimensi...

[Phys. Rev. A 101, 022318] Published Tue Feb 18, 2020

Categories: Journals, Physics

Monitoring scheme against local oscillator attacks for practical continuous-variable quantum-key-distribution systems in complex communication environments

Tue, 2020-02-18 11:00

Author(s): Yi Zheng, Weiqi Liu, Zhengwen Cao, and Jinye Peng

In a practical continuous-variable quantum-key-distribution (CVQKD) system, a strong local oscillator (LO) signal in a quantum channel may be manipulated by eavesdropper Eve to steal information about secret keys through general attacks (e.g., entangling cloner attack or intercept-resend attack) wit...

[Phys. Rev. A 101, 022319] Published Tue Feb 18, 2020

Categories: Journals, Physics

Universal gates for protected superconducting qubits using optimal control

Tue, 2020-02-18 11:00

Author(s): Mohamed Abdelhafez, Brian Baker, András Gyenis, Pranav Mundada, Andrew A. Houck, David Schuster, and Jens Koch

We employ quantum optimal control theory to realize quantum gates for two protected superconducting circuits: the heavy-fluxonium qubit and the 0-π qubit. Utilizing automatic differentiation facilitates the simultaneous inclusion of multiple optimization targets, allowing one to obtain high-fidelity...

[Phys. Rev. A 101, 022321] Published Tue Feb 18, 2020

Categories: Journals, Physics

Time-optimal control of a dissipative qubit

Tue, 2020-02-18 11:00

Author(s): Chungwei Lin, Dries Sels, and Yebin Wang

A formalism based on Pontryagin's maximum principle is applied to determine the time-optimal protocol that drives a general initial state to a target state by a Hamiltonian with limited control, i.e., there is a single control field with bounded amplitude. The coupling between the bath and the qubit...

[Phys. Rev. A 101, 022320] Published Tue Feb 18, 2020

Categories: Journals, Physics

Quantum gradient descent for linear systems and least squares

Fri, 2020-02-14 11:00

Author(s): Iordanis Kerenidis and Anupam Prakash

Quantum machine learning and optimization are exciting new areas that have been brought forward by the breakthrough quantum algorithm of Harrow, Hassidim, and Lloyd for solving systems of linear equations. The utility of classical linear system solvers extends beyond linear algebra as they can be le...

[Phys. Rev. A 101, 022316] Published Fri Feb 14, 2020

Categories: Journals, Physics

Entanglement negativity as a universal non-Markovianity witness

Thu, 2020-02-13 11:00

Author(s): Jan Kołodyński, Swapan Rana, and Alexander Streltsov

In order to engineer an open quantum system and its evolution, it is essential to identify and control the memory effects. These are formally attributed to the non-Markovianity of dynamics that manifests itself by the evolution being indivisible in time, a property which can be witnessed by a nonmon...

[Phys. Rev. A 101, 020303(R)] Published Thu Feb 13, 2020

Categories: Journals, Physics

Universal limitations on implementing resourceful unitary evolutions

Wed, 2020-02-12 11:00

Author(s): Ryuji Takagi and Hiroyasu Tajima

We derive a trade-off relation between accuracy of implementing a desired unitary evolution using a restricted set of free unitaries and the size of the assisting system, in terms of the resource generating and losing capacity of the target unitary. In particular, this relation implies that, for any...

[Phys. Rev. A 101, 022315] Published Wed Feb 12, 2020

Categories: Journals, Physics

Berry phase estimation in gate-based adiabatic quantum simulation

Tue, 2020-02-11 11:00

Author(s): Bruno Murta, G. Catarina, and J. Fernández-Rossier

Gate-based quantum computers can in principle simulate the adiabatic dynamics of a large class of Hamiltonians. Here, we consider the cyclic adiabatic evolution of a parameter in the Hamiltonian. We propose a quantum algorithm to estimate the Berry phase and use it to classify the topological order ...

[Phys. Rev. A 101, 020302(R)] Published Tue Feb 11, 2020

Categories: Journals, Physics

Detecting non-Abelian statistics of topological states on a chain of superconducting circuits

Tue, 2020-02-11 11:00

Author(s): Jun-Yi Cao, Jia Liu, L. B. Shao, and Zheng-Yuan Xue

In view of the fundamental importance and many promising potential applications, non-Abelian statistics of topologically protected states have attracted much attention recently. However, due to the operational difficulties in solid-state materials, experimental realization of non-Abelian statistics ...

[Phys. Rev. A 101, 022313] Published Tue Feb 11, 2020

Categories: Journals, Physics