This paper discusses some statistical properties of the superposition of two coherent states with a vacuum state, such as sub-Poissonian photon statistics and negativity of the Wigner function. Phase probability distr...This paper discusses some statistical properties of the superposition of two coherent states with a vacuum state, such as sub-Poissonian photon statistics and negativity of the Wigner function. Phase probability distribution and phase variance are calculated. Special cases of the constructed superposition states are presented. The results show that depending on the vacuum state coefficient γ and the coherent state coefficient a, it can generate a variety of nonclassical states.展开更多
Phase properties of the even and odd circular states are studied within the Hermitian phase formalism of Pegg and Barnett. Exact analytical formulas for the distribution function and the variance of the phase operator...Phase properties of the even and odd circular states are studied within the Hermitian phase formalism of Pegg and Barnett. Exact analytical formulas for the distribution function and the variance of the phase operator are obtained and used to examine whether or not the even and odd circular states exhibit photon-number squeezing and phase squeezing.展开更多
The effects of decoherence on elliptical states which concern the quantum superposition of N coherent states on an ellipse in the a plane are studied. The characteristic decoherence times are determined. The evolution...The effects of decoherence on elliptical states which concern the quantum superposition of N coherent states on an ellipse in the a plane are studied. The characteristic decoherence times are determined. The evolutions of the Wigner functions associated with these states are investigated theoretically and the losses of nonclassicality as a result of decoherence are discussed. The result shows that the decoherence of elliptical states is slower than circular states relying on the number of coherent states and the amplitude, and the constructed states have a higher resilience to losses.展开更多
The entropy squeezing of an atom with a k-photon in the Jaynes Cummings model is investigated. For comparison, we also study the corresponding variance squeezing and atomic inversion. Analytical results show that entr...The entropy squeezing of an atom with a k-photon in the Jaynes Cummings model is investigated. For comparison, we also study the corresponding variance squeezing and atomic inversion. Analytical results show that entropy squeezing is preferable to variance squeezing for zero atomic inversion. Moreover, for initial conditions of the system the relation between squeezing and photon transition number is also discussed. This provides a theoretical approach to finding out the optimal entropy squeezing.展开更多
We consider a model that contains two coupled superconducting charge qubits by sharing a large Josephson junction. We examine the dynamical properties of the linear entropy of two qubits and the probability of both qu...We consider a model that contains two coupled superconducting charge qubits by sharing a large Josephson junction. We examine the dynamical properties of the linear entropy of two qubits and the probability of both qubits being in an excited state. The results show that the initial mean photon number, the initial phase of the field and the relative phase of the two qubits＇ levels play an important role in the evolution of the linear entropy of the two qubits and the probability.展开更多
A scheme is proposed to generate GHZ state and realize quantum phase gate for superconducting qubits placed in a microwave cavity. This scheme uses resonant interaction between the qubits and the cavity mode, so that ...A scheme is proposed to generate GHZ state and realize quantum phase gate for superconducting qubits placed in a microwave cavity. This scheme uses resonant interaction between the qubits and the cavity mode, so that the interaction time is short, which is important in view of decoherence. In particular, the phase gate can be realized simply with a single interaction between the qubits and the cavity mode. With cavity decay being considered, the fidelity and success probability are both very close to unity.展开更多
We present the measurements and calculations of the absolute total collision cross sections for a room-temperature gas of helium using^(87)Rb atoms confined in either a magneto-optic or a magnetic quadrupole trap.The ...We present the measurements and calculations of the absolute total collision cross sections for a room-temperature gas of helium using^(87)Rb atoms confined in either a magneto-optic or a magnetic quadrupole trap.The loss rates from the magneto-optic trap and the pure magnetic trap are compared and show significant differences.The collision cross sections as a function of trap depth for helium gas are obtained.These findings are significant for extracting the information about the different cross sections when the trap depth is changed.展开更多
We announce the withdrawal of the article entitled“Measurement of Absolute Atomic Collision Cross Section with Helium Using 87Rb Atoms Confined in Magneto-Optic and Magnetic Traps”,which was published in Chinese Phy...We announce the withdrawal of the article entitled“Measurement of Absolute Atomic Collision Cross Section with Helium Using 87Rb Atoms Confined in Magneto-Optic and Magnetic Traps”,which was published in Chinese Physics Letters[28(4)(2011)043401].The first author,Jicheng Wang,had participated in related research with Professor Kirk Madison’s group at the Department of Physics&Astronomy at the University of British Columbia,Canada from September 2008 to February 2010.Even though consent had been granted for some of the experimental data to be used by Jicheng Wang in his own thesis,its publication had not been authorized.We apologize to Professor K.Madison for the misunderstanding,and to Chinese Physics Letters and the readers of Chinese Physics Letters for any inconvenience this mistake may have caused.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 10674038 and 10974039)the National Basic Research Program of China (Grant No. 2006CB302901)
文摘This paper discusses some statistical properties of the superposition of two coherent states with a vacuum state, such as sub-Poissonian photon statistics and negativity of the Wigner function. Phase probability distribution and phase variance are calculated. Special cases of the constructed superposition states are presented. The results show that depending on the vacuum state coefficient γ and the coherent state coefficient a, it can generate a variety of nonclassical states.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10674038 and 10604042)the National Basic Research Program of China (Grant No. 2006CB302901)
文摘Phase properties of the even and odd circular states are studied within the Hermitian phase formalism of Pegg and Barnett. Exact analytical formulas for the distribution function and the variance of the phase operator are obtained and used to examine whether or not the even and odd circular states exhibit photon-number squeezing and phase squeezing.
基金Project supported by the National Basic Research Program of China (Grant No. 2011CB301801)the National Natural Science Foundation of China (Grant No. 10974039)
文摘The effects of decoherence on elliptical states which concern the quantum superposition of N coherent states on an ellipse in the a plane are studied. The characteristic decoherence times are determined. The evolutions of the Wigner functions associated with these states are investigated theoretically and the losses of nonclassicality as a result of decoherence are discussed. The result shows that the decoherence of elliptical states is slower than circular states relying on the number of coherent states and the amplitude, and the constructed states have a higher resilience to losses.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10674038 and 10604042)the National Basic Research Program of China (Grant No. 2006CB302901)
文摘The entropy squeezing of an atom with a k-photon in the Jaynes Cummings model is investigated. For comparison, we also study the corresponding variance squeezing and atomic inversion. Analytical results show that entropy squeezing is preferable to variance squeezing for zero atomic inversion. Moreover, for initial conditions of the system the relation between squeezing and photon transition number is also discussed. This provides a theoretical approach to finding out the optimal entropy squeezing.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10674038 and 10974039, and the National Basic Research Program of China under Grant No 2006CB302901.
文摘We consider a model that contains two coupled superconducting charge qubits by sharing a large Josephson junction. We examine the dynamical properties of the linear entropy of two qubits and the probability of both qubits being in an excited state. The results show that the initial mean photon number, the initial phase of the field and the relative phase of the two qubits＇ levels play an important role in the evolution of the linear entropy of the two qubits and the probability.
基金Project supported by the National Basic Research Program of China (Grant No.2013CBA01702)
文摘A scheme is proposed to generate GHZ state and realize quantum phase gate for superconducting qubits placed in a microwave cavity. This scheme uses resonant interaction between the qubits and the cavity mode, so that the interaction time is short, which is important in view of decoherence. In particular, the phase gate can be realized simply with a single interaction between the qubits and the cavity mode. With cavity decay being considered, the fidelity and success probability are both very close to unity.
基金Supported by the National Basic Research Program of China under Grant No 2011CB301801the National Natural Science Foundation of China under Grant No 10974039jointly supported by the State Scholarship of the China Scholarship Council for Study Abroad.
文摘We present the measurements and calculations of the absolute total collision cross sections for a room-temperature gas of helium using^(87)Rb atoms confined in either a magneto-optic or a magnetic quadrupole trap.The loss rates from the magneto-optic trap and the pure magnetic trap are compared and show significant differences.The collision cross sections as a function of trap depth for helium gas are obtained.These findings are significant for extracting the information about the different cross sections when the trap depth is changed.
文摘We announce the withdrawal of the article entitled“Measurement of Absolute Atomic Collision Cross Section with Helium Using 87Rb Atoms Confined in Magneto-Optic and Magnetic Traps”,which was published in Chinese Physics Letters[28(4)(2011)043401].The first author,Jicheng Wang,had participated in related research with Professor Kirk Madison’s group at the Department of Physics&Astronomy at the University of British Columbia,Canada from September 2008 to February 2010.Even though consent had been granted for some of the experimental data to be used by Jicheng Wang in his own thesis,its publication had not been authorized.We apologize to Professor K.Madison for the misunderstanding,and to Chinese Physics Letters and the readers of Chinese Physics Letters for any inconvenience this mistake may have caused.
