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Coherent-driving-assisted quantum speedup in Markovian channels

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Chinese Physics B 2021年第2期30卷 176-184页

作者： xiang Lu Ying-jie Zhang yun-jie xia Shandong Provincial Key Laboratory of Laser Polarization and Information Technology Department of PhysicsQufu Normal UniversityQufu 273165China

As is well known,the quantum evolution speed of quantum state can never be accelerated in the Markovian regime without any operators on the *** Hamiltonian corrections induced by the action of coherent driving forces are often used to fight dissipative and decoherence mechanisms in *** this reason,considering three noisy channels(the phase-flip channel,the amplitude damping channel and the depolarizing channel),we propose a scheme of speedup evolution of an open system by controlling an external unitary coherent driving operator on the *** is shown that,in the presence of the coherent driving,no-speedup evolution can be transformed into quantum speedup evolution in the Markovian dynamics ***,under the fixed coherent driving strength in the above three noisy channels,the best way to achieve the most degree of quantum speedup for the system has been acquired by rotating the system with appropriate driving direction angles,***,we conclude that the reason for this acceleration is not the nonMarkovian dynamical behavior of the system but due to the oscillation of geometric distance between the initial state and the target final state.

关键词： quantum dynamics control quantum speed limit Markovian dynamics

Steady-state entanglement and heat current of two coupled qubits in two baths without rotating wave approximation

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Chinese Physics B 2019年第6期28卷 72-80页

作者： Mei-Jiao Wang yun-jie xia College of Physics and Engineering Qufu Normal UniversityQufu 273165China Shandong Provincial Key Laboratory of Laser Polarization and Information Technology Qufu Normal UniversityQufu 273165China

We study the steady-state entanglement and heat current of two coupled qubits, in which two qubits are connected with two independent heat baths(IHBs) or two common heat baths(CHBs). We construct the master equation in the eigenstate representation of two coupled qubits to describe the dynamics of the total system and derive the solutions in the steadystate with stronger coupling regime between two qubits than qubit–baths. We do not make the rotating wave approximation(RWA) for the qubit–qubit interaction, and so we are able to investigate the behaviors of the system in both the strong coupling regime and the weak coupling regime, respectively. In an equilibrium bath, we find that the entanglement decreases with the bath temperature and energy detuning increasing under the strong coupling regime. In the weak coupling regime,the entanglement increases with coupling strength increasing and decreases with the bath temperature and energy detuning increasing. In a nonequilibrium bath, the entanglement without RWA is useful for entanglement at lower *** also study the heat currents of the two coupled qubits and their variations with the energy detuning, coupling strength and low temperature. In the strong(weak) coupling regime, the heat current increases(decreases) with coupling strength increasing when the temperature of one bath is lower(higher) than the other, and the energy detuning leads to a positive(negative) effect when the temperature is low(high). In the weak coupling regime, the variation trend of heat current is opposite to that of coupling strength for the IHB case and the CHB case.

关键词： steady-state entanglement equilibrium and nonequilibrium baths heat current rotating wave approximation

Comparative investigation of freezing phenomena for quantum coherence and correlations

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Chinese Physics B 2018年第4期27卷 164-169页

作者： Lian-Wu Yang Wei Han yun-jie xia Shandong Provincial Key Laboratory of Computation Theory Physics Department of Physics and Intbrmation Engineering Jining University Qufu 273155 China Shandong Provincial Key Laboratory of Laser Polarization and Information Technology Department of Physics Qufu Normal University Qufu 273165 China

We show that the freezing phenomenon,exhibited by a specific class of two-qubit state under local nondissipative decoherent evolutions,is a common feature of the relative entropy measure of quantum coherence and *** those measurement outcomes,preserve a constant value in the considered noisy channels,but the condition,property and mechanism of the freezing phenomenon for quantum coherence are different from those of the quantum correlation.

关键词： freezing phenomenon quantum coherence quantum discord

Classical-driving-assisted coherence dynamics and its conservation

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Chinese Physics B 2018年第6期27卷 156-163页

作者： De-Ying Gao Qiang Gao yun-jie xia Shandong Provincial Key Laboratory of Laser Polarization and Information Technology Department of Physics Qufu Normal University Qufu 273165 China College of Dong Chang Liaocheng University Liaocheng 252000 China

We investigate the quantum coherence and quantum entanglement dynamics of a classical driven single atom coupled to a single-mode cavity. It is shown that the transformation between the atomic coherence and the atom-field entanglement exists, and can be improved by adjusting the classical driving field. The joint evolution of two identical single-body systems is also studied. The results show the quantum coherence transfers among composite subsystems, and the coherence conservation of composite subsystems is obtained. Moreover, the classical driving field can be used to suppress the decay of the coherence and entanglement, owing to considering the leaky cavity. The non-Markovian dynamics of the system is also discussed finally.

关键词： quantum coherence classical driving field decoherence

Effect of entanglement embedded in environment on quantum non-Markovianity based on collision model

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Communications in Theoretical Physics 2021年第5期73卷 46-53页

作者： xiao-Ming Li Yong-Xu Chen yun-jie xia Zhong-xiao Man School of Physics and Physical Engineering Shandong Provincial Key Laboratory of Laser Polarization and Information TechnologyQufu Normal UniversityQufu273165China

By means of collision models(CMs)where the environment is simulated by a collection of ancillas consisting of two entangled qubits,we investigate the effects of entanglement in the environment on the non-Markovianity of an open quantum *** CMs are considered in this study,in the first one the open quantum system S directly collides with the environment,while in the second one the system interacts with two intermediate qubits which,in turn,are coupled to the *** show that it is possible to enhance the non-Markovianity by environment entanglement in both *** particular,in the second model,we show that the initial state of the auxiliary qubits can also affect the non-Markovianity of the system and there exists the optimal combination of the initial environmental state and the initial state of auxiliary *** this case,the non-Markovianity can be greatly enhanced.

关键词： collision model entanglement non-Markovianity

Quantum entanglement dynamics based on composite quantum collision model

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Chinese Physics B 2020年第6期29卷 82-89页

作者： xiao-Ming Li Yong-Xu Chen yun-jie xia Qi Zhang Zhong-xiao Man School of Physics and Physical Engineering Shandong Provincial Key Laboratory of Laser Polarization and Information TechnologyQufu Normal UniversityQufu 273165China

By means of composite quantum collision models,we study the entanglement dynamics of a bipartite system,i.e.,two qubits S1 and S2 interacting directly with an intermediate auxiliary qubit SA,while SA is in turn coupled to a thermal *** are concerned with how the intracollisions of the reservoir qubits influence the entanglement *** show that even if the system is initially in the separated state,their entanglement can be generated due to the interaction between the *** the long-time limit,the steady-state entanglement can be generated depending on the initial state of S1 and S2 and the environment *** also study the dynamics of tripartite entanglement of the three qubits S1,S2,and SA when they are initially prepared in the GHZ state and separated state,*** the GHZ initial state,the tripartite entanglement can be maintained for a long time when the collision strength between the environment qubits is sufficiently large.

关键词： entanglement dynamics steady-state entanglement collision model

Protecting the entanglement of two-qubit over quantum channels with memory via weak measurement and quantum measurement reversal

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Chinese Physics B 2020年第11期29卷 203-211页

作者： Mei-Jiao Wang yun-jie xia Yang Yang Liao-Zhen Cao Qin-Wei Zhang Ying-De Li Jia-Qiang Zhao Department of Physics and Optoelectronic Engineering Weifang UniversityWeifang 261061China College of Physics and Engineering Qufu Normal UniversityQufu 273165China Shandong Provincial Key Laboratory of Laser Polarization and Information Technology Qufu Normal UniversityQufu 273165China

Based on the quantum technique of the weak measurement and quantum measurement reversal(WMR),we propose a scheme to protect entanglement for an entangled two-qubit pure state from four typical quantum noise channels with memory,i.e.,the amplitude damping channel,the phase damping channel,the bit flip channel,and the depolarizing *** a given initial state |Ψ>=a |00>+d|11>,it is found that the WMR operation indeed helps to protect entanglement from the above four quantum channels with memory,and the protection effect of WMR scheme is better when the coefficient a is *** the other initial state |φ>=b|01>+c|10>,the effect of the protection scheme is the same regardless of the coefficient b and the WMR operation can protect entanglement in the amplitude damping channel with ***,the protection of entanglement in quantum noise channels without memory in contrast to the results of the channels with memory is more *** |Ψ> or |φ>,we also find that the memory parameters play a significant role in the suppression of entanglement sudden death and the initial entanglement can be drastically *** more important result is that the relationship between the concurrence,the memory parameter,the weak measurement strength,and quantum measurement reversal strength is found through calculation and *** provides a strong basis for the system to maintain maximum entanglement in the nosie channel.

关键词： quantum entanglement weak measurement and quantum measurement reversal quantum channel with memory concurrence

Conditions on converting coherence into entanglement

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Chinese Physics B 2017年第8期26卷 46-49页

作者：杨连武夏云杰 Shandong Provincial Key Laboratory of Laser Polarization and Information Technology Department of PhysicsQufu Normal University Department of Physics and Information Engineering Jining University

The present studies show that any nonzero amount of coherence of a system can be converted into entanglement between the system and an incoherent ancillary system via incoherent operations. According to this conclusion, we study the process of converting coherence into entanglement via a unitary operation where the initial ancillary system is of different quantum state. We find that some other conditions should be satisfied in converting coherence into entanglement. We also study the conditions of coherence consumption of converting coherence into entanglement.

关键词： coherence entanglement conditions

Inexact proximal gradient algorithm with random reshuffling for nonsmooth optimization

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Science China(Information Sciences) 2025年第1期68卷 219-237页

作者： xia JIANG Yanyan FANG xianlin ZENG Jian SUN jie CHEN National Key Lab of Autonomous Intelligent Unmanned Systems School of AutomationBeijing Institute of Technology Beijing Institute of Technology Chongqing Innovation Center School of Electronic and Information Engineering Tongji University

Proximal gradient algorithms are popularly implemented to achieve convex optimization with nonsmooth regularization. Obtaining the exact solution of the proximal operator for nonsmooth regularization is challenging because errors exist in the computation of the gradient; consequently, the design and application of inexact proximal gradient algorithms have attracted considerable attention from researchers. This paper proposes computationally efficient basic and inexact proximal gradient descent algorithms with random reshuffling. The proposed stochastic algorithms take randomly reshuffled data to perform successive gradient descents and implement only one proximal operator after all data pass through. We prove the convergence results of the proposed proximal gradient algorithms under the sampling-without-replacement reshuffling *** computational errors exist in gradients and proximal operations, the proposed inexact proximal gradient algorithms can converge to an optimal solution neighborhood. Finally, we apply the proposed algorithms to compressed sensing and compare their efficiency with some popular algorithms.

关键词： proximal operator random reshuffling inexact computation compressed sensing nonsmooth optimization