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Quantum discord of two-qutrit system under quantum-jump-based feedback control

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Chinese Physics B 2019年第12期28卷 75-81页

作者： Chang Wang mao-fa fang Synergetic Innovation Center for Quantum Effects and Application Key Laboratory of Low-dimensional Quantum Structures and Quantum Control of Ministry of EducationSchool of Physics and ElectronicsHunan Normal UniversityChangsha 410081China

This paper studies quantum discord of two qutrits coupled to their own environments independently and coupled to the same environment simultaneously under quantum-jump-based feedback control. Our results show that spontaneous emission, quantum feedback parameters, classical driving, initial state, and detection efficiency all affect the evolution of quantum discord in a two-qutrit system. We find that under the condition of designing proper quantum-jump-based feedback parameters, quantum discord can be protected and prepared. In the case where two qutrits are independently coupled to their own environments, classical driving, spontaneous emission, and low detection efficiency have negative effect on the protection of quantum discord. For different initial states, it is found that the evolution of quantum discord under the control of appropriate parameters is similar. In the case where two qutrits are simultaneously coupled to the same environment,the classical driving plays a positive role in the generation of quantum discord, but spontaneous emission and low detection efficiency have negative impact on the generation of quantum discord. Most importantly, we find that the steady discord depends on feedback parameters, classical driving, and detection efficiency, but not on the initial state.

关键词： qutrit quantum-jump-based feedback quantum discord

Dynamics of entropic uncertainty for three types of three-level atomic systems under the random telegraph noise

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Chinese Physics B 2020年第5期29卷 459-463页

We study the dynamics of the entropic uncertainty for three types of three-level atomic systems coupled to an environment modeled by random matrices. The results show that the entropic uncertainty in the Ξ-type atomic system is lower than that in the V-type atomic system which is exactly the same as that in the Λ-type atomic system. In addition, the effect of relative coupling strength on entropic uncertainty is opposite in Markov region and non-Markov region, and the influence of a common environment and independent environments in Markov region and non-Markov region is also opposite. One can reduce the entropic uncertainty by decreasing relative coupling strength or placing the system in two separate environments in the Markov case. In the non-Markov case, the entropic uncertainty can be reduced by increasing the relative coupling strength or by placing the system in a common environment.

关键词： entropic uncertainty three-level atom random telegraph noise

Generation of sustained optimal entropy squeezing of a two-level atom via non-Hermitian operation

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Chinese Physics B 2018年第11期27卷 506-511页

作者： Yan-Yi Wang mao-fa fang Synergetic Innovation Center for Quantum Effects and Application and Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education School of Physics and Electronics Hunan Normal University Changsha 410081 China

We investigate the entropy squeezing of a two-level atom in the Jaynes–Cummings model, and provide a scheme to generate the sustained optimal entropy squeezing of the atom via non-Hermitian operation. Our results show that the squeezing degree and the persistence time of entropy squeezing of atomic polarization components greatly depend on the non-Hermiticity intensity in non-Hermitian operation. Especially, under a proper choice of non-Hermiticity parameters, the sustained optimal entropy squeezing of the atom can be generated even though the atom is initially prepared in a no entropy squeezing state.

关键词： entropy squeezing non-Hermitian dynamics quantum optics Jaynes-Cummings model

Quantum speed limit time of a non-Hermitian two-level system

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Chinese Physics B 2020年第3期29卷 89-94页

作者： Yan-Yi Wang mao-fa fang Synergetic Innovation Center for Quantum Effects and Application and Key Laboratory of Low-dimensional Quantum Structures and Quantum Control of Ministry of EducationSchool of Physics and ElectronicsHunan Normal UniversityChangsha 410081China

We investigated the quantum speed limit time of a non-Hermitian two-level system for which gain and loss of energy or amplitude are present. Our results show that, with respect to two distinguishable states of the non-Hermitian system, the evolutionary time does not have a nonzero lower bound. The quantum evolution of the system can be effectively accelerated by adjusting the non-Hermitian parameter, as well as the quantum speed limit time can be arbitrarily small even be zero.

关键词： quantum speed limit time non-Hermitian dynamics quantum optics

Entropy squeezing for a V-type three-level atom interacting with a single-mode field and passing through the amplitude damping channel with weak measurement

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Chinese Physics B 2021年第1期30卷 158-163页

作者： Cui-Yu Zhang mao-fa fang Synergetic Innovation Center for Quantum Effects and Applications Key Laboratory of Low-dimensional Quantum Structures and Quantum Control of Ministry of EducationSchool of Physics and ElectronicsHunan Normal UniversityChangsha 410081China

The entropy squeezing of a V-type three-level atom interacting with a single-mode field and passing through the amplitude damping channel is investigated in detail. Our results show that when coupled to the single-mode field, the atom in appropriate initial states can not only generate obvious entropy squeezing but also keep in the optimal squeezing state,while passing through the amplitude damping channel, the atom can generate entropy squeezing under the control of the weak measurement. Besides, it is proved again that as a measurement method for atomic squeezing, the entropy squeezing is precise and effective. Therefore our work is instructive for experiments in preparing three-level system information resource with ultra-low quantum noise.

关键词： entropy squeezing V-type three-level atom single-mode field weak measurement

Steady and optimal entropy squeezing for three types of moving three-level atoms coupled with a single-mode coherent field

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Chinese Physics B 2021年第1期30卷 164-169页

作者： Wen-Jin Huang mao-fa fang Synergetic Innovation Center for Quantum Effects and Applications Key Laboratory of Low-dimensional Quantum Structures and Quantum Control of Ministry of EducationSchool of Physics and ElectronicsHunan Normal UniversityChangsha 410081China

The entropy squeezing properties of different types of moving three-level atoms coupled with a single-mode coherent field are studied. The influences of the moving velocity and initial states of the three-level atom on the entropy squeezing are discussed. The results show that, the entropy squeezing properties of the three-level atom depend on its initial state, moving velocity, and the type. A stationary three-level atom can not obtain a steady entropy squeezing whatever initial conditions are chosen, while a moving three-level atom can achieve a steady and optimal entropy squeezing through choosing higher velocity and appropriate initial state. Our result provides a simple method for preparing squeezing resources with ultra-low quantum noise of the three-level atomic system without additional any complex techniques.

关键词： entropy squeezing moving three-level atom single-mode coherent field

Controlling the entropic uncertainty and quantum discord in two two-level systems by an ancilla in dissipative environments

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Chinese Physics B 2021年第3期30卷 441-446页

作者： Rong-Yu Wu mao-fa fang Synergetic Innovation Center for Quantum Effects and Application Key Laboratory of Low-dimensional Quantum Structures and Quantum Control of Ministry of EducationSchool of Physics and ElectronicsHunan Normal UniversityChangsha 410081China

The uncertainty principle is a crucial aspect of quantum *** has been shown that the uncertainty principle can be tightened by quantum discord and classical correlation in the presence of quantum *** investigate the control of the entropic uncertainty and quantum discord in two two-level systems by an ancilla in dissipative *** results show that the entropic uncertainty of an observed system can be reduced and the quantum discord between the observed system and the quantum memory system can be enhanced in the steady state of the system by adding an dissipative ***,via preparing the state of the system to the highest excited state with hight fidelity,the entropic uncertainty can be reduced markedly and the quantum discord can be enhanced *** explain these results using the definition of state ***,we present an effective strategy to further reduce the the entropic uncertainty and to enhance the the quantum discord via quantum-jump-based feedback ***,our results may be of importance in the context of quantum information technologies.

关键词： entropic uncertainty quantum discord dissipative environment ancilla

Entropy squeezing for three-level atom interacting with a single-mode field

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Chinese Physics B 2019年第6期28卷 81-86页

作者： Fei-fan Liu mao-fa fang Xiong Xu Synergetic Innovation Center for Quantum Effects and Application Key Laboratory of Low-dimensional Quantum Structures and Quantum Control of Ministry of EducationSchool of Physics and ElectronicsHunan Normal UniversityChangsha 410081China

The entropy squeezing for a three-level atom interacting with a single-model field is studied. A general definition of entropy squeezing for three-level atom is given according to entropic uncertainty relation of three-level system, and the calculation formalism of entropy is derived for a cascade three-level atom. By using numerical calculation, the entropy squeezing properties of a cascade three-level atom are examined. Our results show that, three-level atom can generate obvious entropy squeezing effect via choosing appropriate superposition state of three-level atom. Our results are meaningful for preparing three-level system information resources with ultra-low quantum noise.

关键词： variance squeezing entropy squeezing three-level atom

Protection of entanglement between two V-atoms in a multi-cavity coupling system

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Chinese Physics B 2022年第1期31卷 124-129页

作者： Wen-Jin Huang mao-fa fang Xiong Xu Synergetic Innovation Center for Quantum Effects and Applications Key Laboratory of Low-dimensional Quantum Structures and Quantum Control of Ministry of EducationSchool of Physics and ElectronicsHunan Normal UniversityChangsha 410081China School of Physics and Electronics Hunan Key Laboratory of Super Microstructure and Ultrafast ProcessState Key Laboratory of Powder MetallurgyCentral South UniversityChangsha 410083China

The protection of the entanglement between two V-atoms(EBTVA)in a multi-cavity coupling system is *** whole system consists of two *** two V-atoms are initially in the maximum entangled state and interacts locally with its own dissipative cavity which is coupled to the external cavities with high quality factor(ECWHQF).The results show that,when there is no ECWHQF,the EBTVA can be protected effectively in the case where the V-atom and the dissipative cavity are weak coupled in large detuning,while when there are different numbers n of ECWHQF coupled to two dissipative cavities,by adjusting the parameters of the number n of ECWHQF and the coupling strength k between cavities,the EBTVA can be protected perfectly and *** result provides an effective method for protecting entanglement resources of three-level system.

关键词： V-atom multi-cavity coupling system entanglement negativity