To study the nonclassical effects of the mesoscopic Josephson junction in the presence of a nonclassical microwave, the mesoscopic Josephson junction and the field were both treated quantum mechanically, and the exte...To study the nonclassical effects of the mesoscopic Josephson junction in the presence of a nonclassical microwave, the mesoscopic Josephson junction and the field were both treated quantum mechanically, and the external field approximation was used. It is shown that if the external field is in the coherent state and the state of the junction is initially prepared in the vacuum state, the state of the junction can evolve into a quantum superposition of two coherent states. The Schrdinger cat states can be produced in a mesoscopic Josephson junction.展开更多
We study the interaction between a single-mode quantized field and a quantum system composed of two qubits. We suppose that two qubits initially be prepared in the mixed and separable state, and study how entanglement...We study the interaction between a single-mode quantized field and a quantum system composed of two qubits. We suppose that two qubits initially be prepared in the mixed and separable state, and study how entanglement between two qubits arises in the course of evolution according to the Jaynes-Cummings type interaction with nonclassical radiation field. We also investigate the relation between entanglement and purity of qubit subsystem. We show that different photon statistics have different effects on the dynamical behavior of the qubit subsystem. When the qubits are initially prepared in the maximally mixed and separable state, for coherent state field we cannot find entanglement between two qubits; for squeezed state field entanglement between two qubits exists in several short period of time; for even and odd coherent state fields of large photon number, the dynamical behavior of the entanglement between two qubits shows collapse and revival phenomenon. For odd coherent state field of small photon number, the entanglement with both qubits initially prepared in maximally mixed state can be stronger than that with both qubits initially prepared in pure states. For fields of small photon number, the entanglement strongly depends on the states they are initially prepared in. For coherent state field, and odd and even coherent state fields of large photon number, the entanglement only depends on the purity of the initial state of qubit subsystem. We also show that during the evolution the unentangled state may be purer than the entangled state, and the maximum degree of entanglement may not occur at the time when the qubit subsystem is in the purist state.展开更多
We study the propagation of a quantum probe light in an ensemble of tripod level atoms when the atoms are coupled to two other classical control fields. First we calculate the dispersion properties, such as susceptibi...We study the propagation of a quantum probe light in an ensemble of tripod level atoms when the atoms are coupled to two other classical control fields. First we calculate the dispersion properties, such as susceptibility and group velocity, of the probe light within such an atomic medium under the case of three-photon resonance via the dynamical algebra method of collective atomic excitations. Then we calculate the dispersion of the probe light in the case that two classical control fieMs have the different detunings to the relative atomic transitions. Our results show that in both cases the phenomenon of electromagnetically induced transparency can occur. Especially under the second case, we can find two transparency windows for the probe light.展开更多
A theory of an electron affinity for an ionic cluster is proposed both in a quasiclassical approach and with quantization of a polarization electric field in a nanopartiele. A critical size of the cluster regarding in...A theory of an electron affinity for an ionic cluster is proposed both in a quasiclassical approach and with quantization of a polarization electric field in a nanopartiele. A critical size of the cluster regarding in formation of an electron＇s autolocalized state, dependencies of energy and radius of a polaron on a cluster＇s size are obtained by a variational method. It has been found that binding energy of the electron in the cluster depends on a eluster＇s radius but a radius of electron＇s auto-localization does not depend on the cluster＇s radius and it equals to the polaron radius in a corresponding infinity crystal. A bound state of the electron in a cluster is possible only if the duster＇s radius is more than the polaron radius.展开更多
文摘To study the nonclassical effects of the mesoscopic Josephson junction in the presence of a nonclassical microwave, the mesoscopic Josephson junction and the field were both treated quantum mechanically, and the external field approximation was used. It is shown that if the external field is in the coherent state and the state of the junction is initially prepared in the vacuum state, the state of the junction can evolve into a quantum superposition of two coherent states. The Schrdinger cat states can be produced in a mesoscopic Josephson junction.
文摘We study the interaction between a single-mode quantized field and a quantum system composed of two qubits. We suppose that two qubits initially be prepared in the mixed and separable state, and study how entanglement between two qubits arises in the course of evolution according to the Jaynes-Cummings type interaction with nonclassical radiation field. We also investigate the relation between entanglement and purity of qubit subsystem. We show that different photon statistics have different effects on the dynamical behavior of the qubit subsystem. When the qubits are initially prepared in the maximally mixed and separable state, for coherent state field we cannot find entanglement between two qubits; for squeezed state field entanglement between two qubits exists in several short period of time; for even and odd coherent state fields of large photon number, the dynamical behavior of the entanglement between two qubits shows collapse and revival phenomenon. For odd coherent state field of small photon number, the entanglement with both qubits initially prepared in maximally mixed state can be stronger than that with both qubits initially prepared in pure states. For fields of small photon number, the entanglement strongly depends on the states they are initially prepared in. For coherent state field, and odd and even coherent state fields of large photon number, the entanglement only depends on the purity of the initial state of qubit subsystem. We also show that during the evolution the unentangled state may be purer than the entangled state, and the maximum degree of entanglement may not occur at the time when the qubit subsystem is in the purist state.
基金The,project supported by the China Postdoctoral Science Foundation under Grant No. 2004036309, National Natural Science Foundation of China under Grant Nos. 10447133 and 10574133, and HongKong K.C. Wong Education Foundation
文摘We study the propagation of a quantum probe light in an ensemble of tripod level atoms when the atoms are coupled to two other classical control fields. First we calculate the dispersion properties, such as susceptibility and group velocity, of the probe light within such an atomic medium under the case of three-photon resonance via the dynamical algebra method of collective atomic excitations. Then we calculate the dispersion of the probe light in the case that two classical control fieMs have the different detunings to the relative atomic transitions. Our results show that in both cases the phenomenon of electromagnetically induced transparency can occur. Especially under the second case, we can find two transparency windows for the probe light.
文摘A theory of an electron affinity for an ionic cluster is proposed both in a quasiclassical approach and with quantization of a polarization electric field in a nanopartiele. A critical size of the cluster regarding in formation of an electron＇s autolocalized state, dependencies of energy and radius of a polaron on a cluster＇s size are obtained by a variational method. It has been found that binding energy of the electron in the cluster depends on a eluster＇s radius but a radius of electron＇s auto-localization does not depend on the cluster＇s radius and it equals to the polaron radius in a corresponding infinity crystal. A bound state of the electron in a cluster is possible only if the duster＇s radius is more than the polaron radius.
