We propose a protocol to generate a four-photon polarization-entangled cluster state with cross-Kerr nonlinearity by using the interference of polarized photons. The protocol is based on optical elements, cross-Kerr n...We propose a protocol to generate a four-photon polarization-entangled cluster state with cross-Kerr nonlinearity by using the interference of polarized photons. The protocol is based on optical elements, cross-Kerr nonlinearity, and homodyne measurement, therefore it is feasible with current experimental technology, The success probability of our protocol is optimal, this property makes our protocol more efficient than others in the applications of quantum communication.展开更多
We theoretically study the phase sensitivities of two different phase-shift configurations in an SU(1,1)interferometer with coherent■squeezed vacuum states.According to quantum Cramér-Rao theorem,we analytically...We theoretically study the phase sensitivities of two different phase-shift configurations in an SU(1,1)interferometer with coherent■squeezed vacuum states.According to quantum Cramér-Rao theorem,we analytically obtain the ultimate phase sensitivities for two types of phase shift accumulating in one-and two-arm.Compared with the case of one-arm phase shift,the model with phase shift encoding in both arms may provide a better sensitivity when the strength of squeezed vacuum state is large enough.Furthermore,we discuss the achievable sensitivities with the homodyne measurement by invoking of error-propagation formula.In addition,we study the effect of internal and outernal photon losses on the phase sensitivity of the SU(1,1)interferometer and find that the unbalanced interferometer is helpful to improve precision even with high external losses.展开更多
We propose two schemes for preparing four-photon cluster state through cross-Kerr nonlinearity. Two coherent fields interact when they enter a nonlinear Kerr medium. If the interaction time is chosen appropriately in ...We propose two schemes for preparing four-photon cluster state through cross-Kerr nonlinearity. Two coherent fields interact when they enter a nonlinear Kerr medium. If the interaction time is chosen appropriately in each Kerr medium, four-photon cluster state can be generated based on the results of two homodyne detectors in the first scheme. These schemes only use Kerr medium and homodyne measurements on coherent light fields, which can be effciently made in quantum optical laboratories. In addition, weak cross-Kerr nonlinearity is sufficient. All of the properties make these schemes feasible in experiments.展开更多
We consider the system consisting of two qubits collectively damped, with the output being unit-efficiency measured and subsequently fed back to control the system state. Our primary goal in this paper is （i） to sol...We consider the system consisting of two qubits collectively damped, with the output being unit-efficiency measured and subsequently fed back to control the system state. Our primary goal in this paper is （i） to solve the feedback-modified master equation, （ii） to demonstrate the ability of feedback control based on the solutions, and （iii） to pick out different steady states by choosing different driving strengths and feedback strengths to counteract the effects of both damping and the measurement back-action on the system. We further investigate some properties of the equilibrium steady state, its distribution probability and entanglement vs. the driving and feedback amplitudes. We find that in our feedback model feedback plays a negative role in producing entanglement.展开更多
A scheme is proposed for generating a multiphoton entangled cluster state among four modes. The scheme only uses Kerr medium, beam splitter and homodyne measurements on coherent light fields, which can be efficiently ...A scheme is proposed for generating a multiphoton entangled cluster state among four modes. The scheme only uses Kerr medium, beam splitter and homodyne measurements on coherent light fields, which can be efficiently made in quantum optical laboratories. The photon in the signal mode is prepared in a superposition state of the vacuum state and one-photon state while the probe beam is initially set in a coherent state superposition. The strong probe mode interacts successively with multiple signal-mode photons, each causing a conditional phase rotation in the probe mode. Subsequent momentum quadrature homodyne measurement of the probe mode will project the photons in the signal mode into the desired entangled states. It is shown that under certain conditions, the four-photon cluster state can be generated with high fidelity and high success probability, and the scheme is feasible by current experimental technology.展开更多
Different from the traditional way of using piezoelectric （PZT）phase shifter to measure phase difference, a new method is designed to calculate it between signals in the two arms of a homodyne fiber interferometer. ...Different from the traditional way of using piezoelectric （PZT）phase shifter to measure phase difference, a new method is designed to calculate it between signals in the two arms of a homodyne fiber interferometer. A simple homodyne fiber interferometer system is then established to measure the interference photoeurrent and the photocurrents from the two fiber arms generated by the signal power on a temperature control plat. The homodyne fiber interferometer system is composed of fiber and sensitive to the variation of temperature. Thus, is necessary to study the temperature characteristics in the phase measurement of homodyne fiber interferometer. The experimental results show that the variation of the phase difference of signals in the two fiber arms is proportional to the variation of temperature.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 61068001 and 11064016)
文摘We propose a protocol to generate a four-photon polarization-entangled cluster state with cross-Kerr nonlinearity by using the interference of polarized photons. The protocol is based on optical elements, cross-Kerr nonlinearity, and homodyne measurement, therefore it is feasible with current experimental technology, The success probability of our protocol is optimal, this property makes our protocol more efficient than others in the applications of quantum communication.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11747161 and 11974189the China Postdoctoral Science Foundation under Grant No.2018M642293
文摘We theoretically study the phase sensitivities of two different phase-shift configurations in an SU(1,1)interferometer with coherent■squeezed vacuum states.According to quantum Cramér-Rao theorem,we analytically obtain the ultimate phase sensitivities for two types of phase shift accumulating in one-and two-arm.Compared with the case of one-arm phase shift,the model with phase shift encoding in both arms may provide a better sensitivity when the strength of squeezed vacuum state is large enough.Furthermore,we discuss the achievable sensitivities with the homodyne measurement by invoking of error-propagation formula.In addition,we study the effect of internal and outernal photon losses on the phase sensitivity of the SU(1,1)interferometer and find that the unbalanced interferometer is helpful to improve precision even with high external losses.
基金The National Natural Science Foundation of China(11074002)the Doctoral Foundation of the Ministry of Education of China(20103401110003)+1 种基金the Project of Science Research from Education Department of Anhui Province(KJ2012Z345)the Scientific Research Foundation for Young Teachers of Huaibei Normal University(2011xqxm38)
基金National Natural Science Foundation of China under Grant No.10574022the Natural Science Foundation of Fujian Province of China under Grant Nos.2007J0002 and 2007J0197the Foundation for Universities in Fujian Province under Grant No.2007F5041
文摘We propose two schemes for preparing four-photon cluster state through cross-Kerr nonlinearity. Two coherent fields interact when they enter a nonlinear Kerr medium. If the interaction time is chosen appropriately in each Kerr medium, four-photon cluster state can be generated based on the results of two homodyne detectors in the first scheme. These schemes only use Kerr medium and homodyne measurements on coherent light fields, which can be effciently made in quantum optical laboratories. In addition, weak cross-Kerr nonlinearity is sufficient. All of the properties make these schemes feasible in experiments.
基金The Fund for Excellent Young Talents in the Higher Education Institutions of Anhui Province(No.2009SQRZ087)the Scientific Research Foundation for Young Teachers of Huaibei Normal University(No.2011xqxm38)
基金Supported by the National Natural Science Foundation of China under Grant Nos.10775100,10974137 and 10805034the Fund of Theoretical Nuclear Center of HIRFL of Chinathe Scientific Research Foundation of CUIT under Grant No.KYTZ201024
文摘We consider the system consisting of two qubits collectively damped, with the output being unit-efficiency measured and subsequently fed back to control the system state. Our primary goal in this paper is （i） to solve the feedback-modified master equation, （ii） to demonstrate the ability of feedback control based on the solutions, and （iii） to pick out different steady states by choosing different driving strengths and feedback strengths to counteract the effects of both damping and the measurement back-action on the system. We further investigate some properties of the equilibrium steady state, its distribution probability and entanglement vs. the driving and feedback amplitudes. We find that in our feedback model feedback plays a negative role in producing entanglement.
基金supported by the National Natural Science Foundation of China (Grant No. 11074002)the Doctoral Foundation of the Ministry of Education of China (Grant No. 20103401110003)the Personal Development Foundation of Anhui Province (Grant No. 2008Z018)
文摘A scheme is proposed for generating a multiphoton entangled cluster state among four modes. The scheme only uses Kerr medium, beam splitter and homodyne measurements on coherent light fields, which can be efficiently made in quantum optical laboratories. The photon in the signal mode is prepared in a superposition state of the vacuum state and one-photon state while the probe beam is initially set in a coherent state superposition. The strong probe mode interacts successively with multiple signal-mode photons, each causing a conditional phase rotation in the probe mode. Subsequent momentum quadrature homodyne measurement of the probe mode will project the photons in the signal mode into the desired entangled states. It is shown that under certain conditions, the four-photon cluster state can be generated with high fidelity and high success probability, and the scheme is feasible by current experimental technology.
基金supported by the National Natural Science Foundation of China (60372061)Basic Fund for the Scientific Research Project of Jilin University (200903296)
文摘Different from the traditional way of using piezoelectric （PZT）phase shifter to measure phase difference, a new method is designed to calculate it between signals in the two arms of a homodyne fiber interferometer. A simple homodyne fiber interferometer system is then established to measure the interference photoeurrent and the photocurrents from the two fiber arms generated by the signal power on a temperature control plat. The homodyne fiber interferometer system is composed of fiber and sensitive to the variation of temperature. Thus, is necessary to study the temperature characteristics in the phase measurement of homodyne fiber interferometer. The experimental results show that the variation of the phase difference of signals in the two fiber arms is proportional to the variation of temperature.
