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decoherence from a spin chain with Dzyaloshinskii-Moriya interaction

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Chinese Physics B 2012年第10期21卷 79-86页

作者：颜益营秦立国田立君 Department of Physics Shanghai University

We study the dynamics of quantum discord and entanglement for two spin qubits coupled to a spin chain with Dzyaloshinsky Moriya interaction. In the case of a two-qubit with an initial pure state, quantum correlations decay to zero at the critical point of the environment in a very short time. In the case of a two-qubit with initial mixed state, it is found that quantum discord may get maximized due to the quantum critical behavior of the environment, while entanglement vanishes under the same condition. Besides, we observed a sudden transition between classical and quantum decoherence when only a single qubit interacts with the environment. The effects of Dzyaloshinsky-Moriya interaction on quantum correlations are considered in the two cases. The decay of quantum correlations is always strengthened by Dzyaloshinsky Moriya interaction.

关键词： quantum discord entanglement decoherence

decoherence in optimized quantum random-walk search algorithm

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Chinese Physics B 2015年第8期24卷 197-202页

作者：张宇超鲍皖苏汪翔付向群 Zhengzhou Information Science and Technology Institute Synergetic Innovation Center of Quantum Information and Quantum Physics University of Science and Technology of China

This paper investigates the effects of decoherence generated by broken-link-type noise in the hypercube on an optimized quantum random-walk search algorithm. When the hypercube occurs with random broken links, the optimized quantum random-walk search algorithm with decoherence is depicted through defining the shift operator which includes the possibility of broken links. For a given database size, we obtain the maximum success rate of the algorithm and the required number of iterations through numerical simulations and analysis when the algorithm is in the presence of decoherence. Then the computational complexity of the algorithm with decoherence is obtained. The results show that the ultimate effect of broken-link-type decoherence on the optimized quantum random-walk search algorithm is negative.

关键词： quantum search algorithm quantum random walk decoherence

decoherence dynamics of a charge qubit coupled to the noise bath

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Chinese Physics B 2013年第7期22卷 50-55页

作者：杨芹英梁宝龙王继锁 School of Physics Science and Information Engineering Liaocheng University College of Physics and Engineering Qufu Normal University

By virtue of the canonical quantization method, we present a quantization scheme for a charge qubit based on the superconducting quantum interference device （SQUID）, taking the self-inductance of the loop into account. Under reasonable short-time approximation, we study the effect of decoherence in the ohmic case by employing the response function and the norm. It is confirmed that the decoherence time, which depends on the parameters of the circuit components, the coupling strength, and the temperature, can be as low as several picoseconds, so there is enough time to record the information.

关键词： charge qubit decoherence response function norm

decoherence Induced by Spin Chain Environment

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Chinese Physics Letters 2006年第10期23卷 2648-2651页

作者：王林成崔海涛衣学喜 Department of Physics Dalian University of Technology Dalian 116024

We study the decoherence process of an exact solvable model that consists of a central spin-1/2 coupling to the surrounding anisotropy spin-1/2 chain in transverse fields. The Loschrnidt echo is calculated to study the character of decoherence with different degree of anisotropy. Our results show that the degree of anisotropy γ greatly affects the decoherence process of the central spin-system when the spin chain is in weak transverse fields, but it gives weak effect in the strong transverse field. The decoherence process of the central system changed dramatically along the line of the critical points, and this may be explained as the reflection of quantum phase transitions.

关键词： decoherence Spin Chain Environment quantum

decoherence for a two-qubit system in a spin-chain environment

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Chinese Physics B 2018年第9期27卷 175-179页

作者： Yang Yangl An-Min Wang Lian-Zhen Cao Jia-Qiang Zhao Huai-Xin Lu Department of Physics and Optoelectronic Engineering Weifang UniversityWeifang 261061China Department of Modern Physics University of Science and Technology of ChinaHefei 230026China

The quantum coherence and correlation dynamics for a two-qubit system in the Ising spin-chain environment are studied. A sudden change of coherence is found near the critical point, which provides us with an effective way to detect the quantum phase transition. By studying the relationship between quantum discord and coherence, we find that coherence displays the behavior of classical correlation for t 〈 t0, and of quantum discord for t 〉 t0, where t0 is the time-point of a sudden transition between classical and quantum decoherence.

关键词： quantum coherence quantum discord decoherence

decoherence-free subspace and entanglement sudden death of multi-photon polarization states in fiber channels

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Communications in Theoretical Physics 2023年第4期75卷 24-33页

作者： Yiwen Liu School of Physics Peking UniversityBeijing10087China

The construction of quantum networks requires long-distance teleportation of multi-qubit entangled ***,we investigate the entanglement dynamics of GHZ and W states in fiber *** a fiber channel,the two most important phenomena that affect polarization entanglement are polarization mode dispersion(PMD)and polarization-dependent loss(PDL).We theoretically characterize how PMD and PDL vectors affect three-qubit *** particular,upon quantifying the entanglement at the output states using concurrence and entanglement witnesses,we reveal the occurrence of entanglement sudden death and the appearance of decoherence-free subspaces in tripartite ***,we explore the evolution of GHZ and W state with an arbitrary number of photons in a fiber network and discuss the decoherence mechanism of the 4-party cluster state.

关键词： multi-photon entanglement decoherence polarization mode dispersion polarizationdependent loss decoherence-free subspace entanglement sudden death

decoherence of two-qubit system in a non-Markovian squeezed reservoir

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Chinese Physics B 2009年第2期18卷 597-603页

作者：王发强张智明梁瑞生 Laboratory of Photonic Information Technology School of Information and Photoelectronic Science and Engineering South China Normal University

The decoherence of two initially entangled qubits coupled with a squeezed vacuum cavity separately is investigated exactly. The results show that, first, in principle, the disentanglement time decreases with the increase of squeeze parameter r, due to the augmenting of average photon number of every mode in the squeezed vacuum cavity. Second, there appear entanglement revivals after the complete disentanglement for the ease of even parity initial Bell state, while there occur the entanglement decrease and the entanglement revival before the complete disentanglement for the case of odd parity initial Bell state. The results are quite different from those for the case of qubits in a vacuum cavity.

关键词： decoherence squeezed reservoir non-Markovian qubit

decoherence Effect in An Anisotropic Two-Qubit Heisenberg XYZ Model with Inhomogeneous Magnetic Field

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Communications in Theoretical Physics 2010年第6期53卷 1053-1058页

作者：陈涛单传家李金星刘继兵刘堂昆黄燕霞 College of Physics and Electronic Science Hubei Normal University

Taking the decoherence effect into account, the entanglement evolution of a two-qubit anisotropic Heisenberg XYZ chain in the presence of inhomogeneous magnetic field is investigated. The time evolution of concurrence is studied for the initial state cos θ｜01）＋ sin θ｜10） at zero temperature. The influences of inhomogeneous magnetic field, anisotropic parameter and decoherence on entanglement dynamic are addressed in detail, and a concurrence formula of the steady state is found. It is shown that the entanglement sudden death （ESD） and entanglement sudden birth （ESB） appear with the decoherence effect, and the stable concurrence depends on the uniform magnetic field B, anisotropic parameter △ and environment coupling strength γ, which is independent of different initial states and nonuniform magnetic field b.

关键词： Heisenberg model thermal entanglement concurrence decoherence inhomogeneous magneticfield

decoherence,Orbit,and Classical Linear Frequency Entropy:Quantum-Classical Correspondence

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Communications in Theoretical Physics 2009年第8期52卷 221-225页

作者： ZHANG Shi-Hui JIE Quan-Lin WANG Zhuo Department of Physics Wuhan University Wuhan 430072 China

The decoherence process is analyzed for an open quantum system that is classically chaotic,with a classicallinear frequency entropy developed to measure the stability of classical motion,Investigation shows that the decoherencemeasured by the rate of quantum linear entropy production varies significantly with both the underlying classical orbitsand the classical linear frequency *** correspondence is also supported by the further investigation on theLoschmidt Echo.

关键词： decoherence orbit rate of linear entropy classical linear frequency entropy