By introducing the von Neumann entropy as a measure of the extent of noise, this paper discusses the entropy evolution in a two-level quantum feedback controlled system. The results show that the feedback control can ...By introducing the von Neumann entropy as a measure of the extent of noise, this paper discusses the entropy evolution in a two-level quantum feedback controlled system. The results show that the feedback control can induce the reduction of the degree of noise, and different control schemes exhibit different noise controlling ability, the extent of the reduction also related with the position of the target state on the Bloch sphere. It is shown that the evolution of entropy can provide a real time noise observation and a systematic guideline to make reasonable choice of control strategy.展开更多
This paper proposes the continuous controller design method for quantum Shannon entropy, which can continuously drive the entropy to track a desired trajectory. We also analyzed the controllability of Shannon entropy ...This paper proposes the continuous controller design method for quantum Shannon entropy, which can continuously drive the entropy to track a desired trajectory. We also analyzed the controllability of Shannon entropy in very short time interval. Simulations are done on five dimensional quantum system, which can verify the validation of the method.展开更多
We study the entanglement of dressed atom and its spontaneous emission in a three-level A-type closed-loop atomic system in a multi-photon resonance condition and beyond it. It is shown that the von Neumann entropy in...We study the entanglement of dressed atom and its spontaneous emission in a three-level A-type closed-loop atomic system in a multi-photon resonance condition and beyond it. It is shown that the von Neumann entropy in such a system is phase-dependent, and it can be controlled by either the intensity or relative phase of applied fields. It is demonstrated that for the special case of the Rabi frequency of applied fields, the system is disentangled. In addition, we take into account the effect of Doppler broadening on the entanglement and it is found that a suitable choice of laser propagation direction allows us to obtain the steady state degree of entanglement （DEM） even in the presence of the Doppler effect.展开更多
A Cooper-pair box biased by a classical voltage and also irradiated by a squeezed state field is considered in order to find new ways to quantum communication and calculation. The quantum dynamics of the Cooper-pair b...A Cooper-pair box biased by a classical voltage and also irradiated by a squeezed state field is considered in order to find new ways to quantum communication and calculation. The quantum dynamics of the Cooper-pair box and the entanglement which is the core theoretics of quantum communication and calculation is investigated in this system, which is related to the squeezing parameter of the squeezed state, A model of Hamiltonian which represents the interaction between box and quantum field is introduced. Finally, the relationship between the entanglement and the squeezing parameter of the squeezed state is demonstrated.展开更多
We have investigated the evolution of the atomic quantum entropy and the entanglement of atom-photon in the system with competing k-photon and l-photon transitions by means of fully quantum theory, and examined the ef...We have investigated the evolution of the atomic quantum entropy and the entanglement of atom-photon in the system with competing k-photon and l-photon transitions by means of fully quantum theory, and examined the effects of competing photon numbers （k and l）, the relative coupling strength between the atom and the two-mode field （A/g）, and the initial photon number of the field on the atomic quantum entropy and the entanglement of atom-photon. The results show that the multiphoton competing transitions or the large relative coupling strength can lead to the strong entanglement between atoms and photons. The maximal atom-photon entanglement can be prepared via the appropriate selection of system parameters and interaction time.展开更多
A Hamiltonian which represents the interaction between a single Cooper-pair box and two quantized electromagnetic fields is considered in order to find new ways for quantum information. The wave function in Schrodinge...A Hamiltonian which represents the interaction between a single Cooper-pair box and two quantized electromagnetic fields is considered in order to find new ways for quantum information. The wave function in Schrodinger picture is obtained. The evolution of the entropy of the box as a function of the scaled time is ploted to measure the entanglement between the box and the fields. It is found that the entanglement is sensitive to the detuning between the Josephson energy and the fields frequency, increasing the detuning can decrease the entanglement.展开更多
基金Project supported by the National Natural Science Foundation of China （Grant No 10374025）.
文摘By introducing the von Neumann entropy as a measure of the extent of noise, this paper discusses the entropy evolution in a two-level quantum feedback controlled system. The results show that the feedback control can induce the reduction of the degree of noise, and different control schemes exhibit different noise controlling ability, the extent of the reduction also related with the position of the target state on the Bloch sphere. It is shown that the evolution of entropy can provide a real time noise observation and a systematic guideline to make reasonable choice of control strategy.
文摘This paper proposes the continuous controller design method for quantum Shannon entropy, which can continuously drive the entropy to track a desired trajectory. We also analyzed the controllability of Shannon entropy in very short time interval. Simulations are done on five dimensional quantum system, which can verify the validation of the method.
文摘We study the entanglement of dressed atom and its spontaneous emission in a three-level A-type closed-loop atomic system in a multi-photon resonance condition and beyond it. It is shown that the von Neumann entropy in such a system is phase-dependent, and it can be controlled by either the intensity or relative phase of applied fields. It is demonstrated that for the special case of the Rabi frequency of applied fields, the system is disentangled. In addition, we take into account the effect of Doppler broadening on the entanglement and it is found that a suitable choice of laser propagation direction allows us to obtain the steady state degree of entanglement （DEM） even in the presence of the Doppler effect.
文摘A Cooper-pair box biased by a classical voltage and also irradiated by a squeezed state field is considered in order to find new ways to quantum communication and calculation. The quantum dynamics of the Cooper-pair box and the entanglement which is the core theoretics of quantum communication and calculation is investigated in this system, which is related to the squeezing parameter of the squeezed state, A model of Hamiltonian which represents the interaction between box and quantum field is introduced. Finally, the relationship between the entanglement and the squeezing parameter of the squeezed state is demonstrated.
基金Project supported by the National Natural Science Foundation of China （Grant No 10374025）.
文摘We have investigated the evolution of the atomic quantum entropy and the entanglement of atom-photon in the system with competing k-photon and l-photon transitions by means of fully quantum theory, and examined the effects of competing photon numbers （k and l）, the relative coupling strength between the atom and the two-mode field （A/g）, and the initial photon number of the field on the atomic quantum entropy and the entanglement of atom-photon. The results show that the multiphoton competing transitions or the large relative coupling strength can lead to the strong entanglement between atoms and photons. The maximal atom-photon entanglement can be prepared via the appropriate selection of system parameters and interaction time.
文摘A Hamiltonian which represents the interaction between a single Cooper-pair box and two quantized electromagnetic fields is considered in order to find new ways for quantum information. The wave function in Schrodinger picture is obtained. The evolution of the entropy of the box as a function of the scaled time is ploted to measure the entanglement between the box and the fields. It is found that the entanglement is sensitive to the detuning between the Josephson energy and the fields frequency, increasing the detuning can decrease the entanglement.
