We propose a theoretical scheme for realizing the general conditional phase shift gate of charge qubitssituated in a high-Q superconducting transmission line resonator.The phase shifting angle can be tuned from 0 to 2...We propose a theoretical scheme for realizing the general conditional phase shift gate of charge qubitssituated in a high-Q superconducting transmission line resonator.The phase shifting angle can be tuned from 0 to 2n bysimply adjusting the qubit-resonator detuning and the interaction time.Based on this gate proposal,we give a detailedprocedure to implement the three-qubit quantum Fourier transform with circuit quantum electrodynamics (QED).Acareful analysis of the decoherence sources shows that the algorithm can be achieved with a high fidelity using currentcircuit QED techniques.展开更多
Recently,Zhou et al.[Phys.Rev.A 79 (2009) 044304] proposed a scheme for transferring three-dimensionalquantum states between remote atomic qubits confined in cavities connected by fibers through adiabatic passage.Inor...Recently,Zhou et al.[Phys.Rev.A 79 (2009) 044304] proposed a scheme for transferring three-dimensionalquantum states between remote atomic qubits confined in cavities connected by fibers through adiabatic passage.Inorder to avoid the decoherence due to spontaneous emission,Zhou et ad.utilized the large detuning atom-field interaction.In the present paper,we discuss the influence of dissipation on the scheme in both the resonant atom-field interactioncase and the large detuning case.We numerically analyze the success probability and the transferring fidelity.It is shownthat the resonant case is a preferable choice for the technique of the stimulated Raman adiabatic passage (STIRAP) dueto the shorter operation time and the smaller probability of dissipation.展开更多
The properties of the system near the instability boundary are very sensitive to external disturbances, which is important for amplifying some physical effects or improving the sensing accuracy. In this paper, the qua...The properties of the system near the instability boundary are very sensitive to external disturbances, which is important for amplifying some physical effects or improving the sensing accuracy. In this paper, the quantum properties near the instability boundary in a simple optomechanical system have been studied by numerical simulation. Calculations show that the transitional region connecting the Gaussian states and the ring states when crossing the boundary is sometimes different from the region centered on the boundary line, but it is more essential. The change of the mechanical Wigner function in the transitional region directly reflects its bifurcation behavior in classical dynamics. Besides, quantum properties, such as mechanical second-order coherence function and optomechanical entanglement, can be used to judge the corresponding bifurcation types and estimate the parameter width and position of the transitional region. The non-Gaussian transitional states exhibit strong entanglement robustness, and the transitional region as a boundary ribbon can be expected to replace the original classical instability boundary line in future applications.展开更多
A simple scheme is proposed to generate the W state of N A-type neutral atoms trapped in an optical cavity via Raman transition. Conditional on no photon leakage from the cavity, the N-qubit W state can be prepared pe...A simple scheme is proposed to generate the W state of N A-type neutral atoms trapped in an optical cavity via Raman transition. Conditional on no photon leakage from the cavity, the N-qubit W state can be prepared perfectly by turning on a classical coupling field for an appropriate time. Compared with the previous ones, our scheme requires neither individual laser addressing of the atoms, nor demand for controlling N atoms to go through an optical cavity simultaneously with a constant velocity. We investigate the influence of cavity decay using the quantum jump approach and show that the preparation time decreases and the success probability increases with atom number because of a collective enhancement of the coupling.展开更多
In order to understand our previous numerical finding that steady-state entanglement along the instability boundary remains unchanged in a three-mode optomechanical system[Phys.Rev.A 101023838(2020)],we investigate in...In order to understand our previous numerical finding that steady-state entanglement along the instability boundary remains unchanged in a three-mode optomechanical system[Phys.Rev.A 101023838(2020)],we investigate in detail the boundary entanglement in a simpler two-mode optomechanical system.Studies show that both the mechanism to generate entanglement and the parameter dependence of boundary entanglement are quite similar in these two models.Therefore,the two-mode system has captured the main features in the three-mode system.With the help of analytical calculations and discussing in a much bigger parameter interval,we find that the unchanging behavior previously discovered is actually an extremely slow changing behavior of the boundary entanglement function,and most importantly,this nearly invariant boundary entanglement is a general phenomenon via parametric down conversion process in the weak dissipation regime.This is by itself interesting as threshold quantum signatures in optomechanical phonon lasers,or may have potential value in related applications based on boundary quantum properties.展开更多
基金Supported by the Foundation for the Author of National Excellent Doctoral Dissertation of China under Grant No. 200524the Program for New Century Excellent Talents of China under Grant No. 06-0920
文摘We propose a theoretical scheme for realizing the general conditional phase shift gate of charge qubitssituated in a high-Q superconducting transmission line resonator.The phase shifting angle can be tuned from 0 to 2n bysimply adjusting the qubit-resonator detuning and the interaction time.Based on this gate proposal,we give a detailedprocedure to implement the three-qubit quantum Fourier transform with circuit quantum electrodynamics (QED).Acareful analysis of the decoherence sources shows that the algorithm can be achieved with a high fidelity using currentcircuit QED techniques.
文摘Recently,Zhou et al.[Phys.Rev.A 79 (2009) 044304] proposed a scheme for transferring three-dimensionalquantum states between remote atomic qubits confined in cavities connected by fibers through adiabatic passage.Inorder to avoid the decoherence due to spontaneous emission,Zhou et ad.utilized the large detuning atom-field interaction.In the present paper,we discuss the influence of dissipation on the scheme in both the resonant atom-field interactioncase and the large detuning case.We numerically analyze the success probability and the transferring fidelity.It is shownthat the resonant case is a preferable choice for the technique of the stimulated Raman adiabatic passage (STIRAP) dueto the shorter operation time and the smaller probability of dissipation.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11574398, 12174448, 12174447, 11904402, 12074433, 11871472, and 12004430)。
文摘The properties of the system near the instability boundary are very sensitive to external disturbances, which is important for amplifying some physical effects or improving the sensing accuracy. In this paper, the quantum properties near the instability boundary in a simple optomechanical system have been studied by numerical simulation. Calculations show that the transitional region connecting the Gaussian states and the ring states when crossing the boundary is sometimes different from the region centered on the boundary line, but it is more essential. The change of the mechanical Wigner function in the transitional region directly reflects its bifurcation behavior in classical dynamics. Besides, quantum properties, such as mechanical second-order coherence function and optomechanical entanglement, can be used to judge the corresponding bifurcation types and estimate the parameter width and position of the transitional region. The non-Gaussian transitional states exhibit strong entanglement robustness, and the transitional region as a boundary ribbon can be expected to replace the original classical instability boundary line in future applications.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10504042)the Key Laboratory of Low Dimensional Quantum Structures and Quantum Control (Hunan Normal University)Ministry of Education of China (Grant No.QSQC0902)
文摘A simple scheme is proposed to generate the W state of N A-type neutral atoms trapped in an optical cavity via Raman transition. Conditional on no photon leakage from the cavity, the N-qubit W state can be prepared perfectly by turning on a classical coupling field for an appropriate time. Compared with the previous ones, our scheme requires neither individual laser addressing of the atoms, nor demand for controlling N atoms to go through an optical cavity simultaneously with a constant velocity. We investigate the influence of cavity decay using the quantum jump approach and show that the preparation time decreases and the success probability increases with atom number because of a collective enhancement of the coupling.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11574398,11904402,12074433,and 12004430)the National Basic Research Program of China(Grant No.2016YFA0301903).
文摘In order to understand our previous numerical finding that steady-state entanglement along the instability boundary remains unchanged in a three-mode optomechanical system[Phys.Rev.A 101023838(2020)],we investigate in detail the boundary entanglement in a simpler two-mode optomechanical system.Studies show that both the mechanism to generate entanglement and the parameter dependence of boundary entanglement are quite similar in these two models.Therefore,the two-mode system has captured the main features in the three-mode system.With the help of analytical calculations and discussing in a much bigger parameter interval,we find that the unchanging behavior previously discovered is actually an extremely slow changing behavior of the boundary entanglement function,and most importantly,this nearly invariant boundary entanglement is a general phenomenon via parametric down conversion process in the weak dissipation regime.This is by itself interesting as threshold quantum signatures in optomechanical phonon lasers,or may have potential value in related applications based on boundary quantum properties.
