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Disorder and decoherence in coined quantum walks

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Chinese Physics B 2013年第11期22卷 64-75页

作者：张融秦豪唐宝薛鹏 Department of Physics Southeast University State Key Laboratory of Precision Spectroscopy East China Normal University

This article aims to provide a review on quantum walks. Starting form a basic idea of discrete-time quantum walks, we will review the impact of disorder and decoherence on the properties of quantum walks. The evolution of the standard quantum walks is deterministic and disorder introduces randomness to the whole system and change interference pattern leading to the localization effect. Whereas, decoherence plays the role of transmitting quantum walks to classical random walks.

关键词： quantum walk disorder decoherence

Topological Effect of Reduced Quantum Trajectory in Coherence and decoherence

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Communications in Theoretical Physics 2010年第9期54卷 433-438页

作者：史旭光段一士秦志杰 College of Science Beijing Forestry University Institude of Theoretical Physics Lanzhou University School of Physics and Engineering Zhengzhou University

The topological expression of the reduced quantum trajectory is given by using C-mapping topological current theory. The topological expression is used in study of the coherence and the decoherence. We find the expression of vorticity for decoherence has a similar form as that for coherence. A topological reason leading to the decoherence is given and a new parameter is defined to indicate the coherence degree. The parameter is different from the damping factor because it relates to the topological structure of the reduced quantum trajectory.

关键词： coherence decoherence topology vorticity

Single molecular shuttle-junction： Shot noise and decoherence

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Frontiers of physics 2015年第1期10卷 59-86页

作者： Wenxi Lai Chao Zhang Zhongshui Ma School of Physics Peking University Beijing 100871 China Beijing Computational Science Research Center Beijing 100084 China School of Physics University of Wollongong New South Wales 2522 Australia Collaborative Innovation Center of Quantum Matter Beijing 100871 China

Single molecular shuttle-junction is one kind of nanoscale electromechanical tunneling system. In this junction, a molecular island oscillates depending on its charge occupation, and this charge dependent oscillation leads to modulation of electron tunneling through the molecular island. This paper reviews recent development on the study of current, shot noise and decoherence of electrons in the single molecular shuttle-junction. We will give detailed discussion on this topic using the typical system model, the theory of fully quantum master equation and the Aharonov-Bohm interferometer.

关键词： molecular shuttle-junction master equation shot noise decoherence

A Quantum Dynamical Mode for the Control of decoherence

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Communications in Theoretical Physics 2005年第1期43卷 59-64页

作者： HuangWan-Xia WangQin-Mou InstituteofPhysicsDepartmentandElectronicInformation AnhuiNormalUniversityWuhu241000China

We present a quantum measurement model where the meter is taken to be a squeezed reservoir. life realize decoherence in macroscopic limits using Bogoliubov transformation, and this kind of system-meter coupling has a ... 详细信息

关键词： coherent states displace operators squeezing operators canonical transformation decoherence

Nonclassicality and decoherence of the coherent superposition operation of photon subtraction and addition on the squeezed state

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Chinese Physics B 2013年第3期22卷 163-168页

作者：徐莉娟谭国斌马善钧郭琴 College of Physics and Communication Electronics Jiangxi Normal University

The statistical properties of m-coherent superposition operation（μa ＋ νa）^m on the single-mode squeezed vacuum state（M-SSVS） and its decoherence in a thermal environment are *** the M-SSVS to a squeezed Hermite polynomial excitation state,we obtain a compact expression for the normalization factor of M-SSVS,which is the Legendre polynomial of the squeezing *** also derive the explicit expression of the Wigner function（WF） of the M-SSVS,and find the negative region of the WF in phase *** decoherence effect on this state is then discussed by deriving the time evolution of the *** the negativity of the WF,the loss of nonclassicality is then discussed.

关键词： nonclassicality decoherence coherent superposition of photon subtraction and addition Wigner function

Robustness of Entanglement During decoherence

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Communications in Theoretical Physics 2014年第11期61卷 667-672页

作者：金光日赵宝奎李红梅陆景彬 College of Physics Jilin University Department of Physics Kim Il Sung University

Finding the most robust entangled states during the whole process of decoherence is a particularly fundamental problem for quantum physics and quantum information processing. In this paper, the decoherence process of two-qubit system under two individual identical decoherence channels is investigated systematically. We find that although the robustness of two-qubit states with same initial entanglement is usually different, the Bell-like states are always the most robust entangled states during decoherence. That is to say, affected by the same amount of noise, the remain entanglement of an arbitrary two-qubit state is not more than that of a Bell-like state with the same initial entanglement.

关键词： decoherence open systems entanglement

Quantum Monty Hall Problem under decoherence

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Communications in Theoretical Physics 2010年第7期54卷 47-54页

作者： Salman Khan M.Ramzan M.K.Khan Department of Physics Quaid-i-Azam University

We study the effect of decoherence on quantum Monty Hall problem under the influence of amplitude damping, depolarizing, and dephasing channels. It is shown that under the effect of decoherence, there is a Nash equilibrium of the game in case of depolarizing channel for Alice＇s quantum strategy. Whereas in case of dephasing noise, the game is not influenced by the quantum channel. For amplitude damping channel, Bob＇s payoffs are found symmetrical about a decoherence of 50% and the maximum occurs at this value of decoherence for his classical strategy. However, it is worth-mentioning that in case of depolarizing channel, Bob＇s classical strategy remains always dominant against any choice of Alice＇s strategy.

关键词： quantum Monty Hall problem decoherence entanglement payoffs

Spin squeezing in Bose-Einstein condensates： Limits imposed by decoherence and non-zero temperature

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Frontiers of physics 2012年第1期7卷 86-97页

作者： Alice Sinatra (1) Jean-Christophe Dornstetter (1) Yvan Castin (1) 1. Laboratoire Kastler Brossel Ecole Normale Supérieure UPMC and CNRS Paris France

We consider dynamically generated spin squeezing in interacting bimodal condensates. We show that particle losses and non-zero temperature effects in a multimode theory completely change the scaling of the best squeezing for large atom numbers. We present the new scalings and we give approximate analytical expressions for the squeezing in the thermodynamic limit. Besides reviewing our recent theoretical results, we give here a simple physical picture of how decoherence acts to limit the squeezing. We show in particular that under certain conditions the decoherence due to losses and non-zero temperature acts as a simple dephasing.

关键词： Bose-Einstein condensate decoherence

Detecting ground-state degeneracy in many-body systems through qubit decoherence

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Frontiers of physics 2017年第1期12卷 77-84页

作者：崔海涛衣学喜 School of Physics and Electric Engineering Anyang Normnal University Anyang 355000 China Center for Quantum Sciences Northeast Normal University Changchun 130023 China

By coupling with a qubit, we demonstrate that qubit decoherence can unambiguously detect the occurrence of ground-state degeneracy in many-body systems. We first demonstrate universality using the two-band model. Consequently, several exemplifications, focused on topological condensed matter systems in one, two, and three dimensions, are presented to validate our proposal. The key point is that qubit decoherence varies significantly when energy bands touch each other at the Fermi surface. In addition, it can partially reflect the degeneracy inside the band. This feature implies that qubit decoherence can be used for reliable diagnosis of ground-state degeneracy.

关键词： decoherence quantum phase transition ground-state degeneracy