Narrow Results

We study the interaction of a moving four-level atom with a single mode cavity field. Involving intensity dependent coupling, the atom-field wave function and the reduced density matrix of the field are obtained when the atom is initially prepared in a coherent superposition of the upper and ground states and the field is initially in a coherent state. The influence of the intensity dependent atom-field coupling and of the detuning on the collapse and revival phenomenon of the time evolution of statistical aspects, such as the mean photon number, the second-order correlation function of the field, the momentum increment and momentum diffusion, are investigated. It is found that, for the nonresonant case, the detuning between the field and the atom has a significant influence which leads to increasing the collapse time with decreasing amplitude. Numerical computations and discussion of the results are presented.

We propose a scheme for entanglement swapping and entanglement concentration without joint measurement by using the two-photon Jaynes-Cummings model. In the scheme, we can generate a maximally entangled pair between two initially uncorrelated atoms or cavities. Furthermore, the entangled state between two cavities is found to be a photon entanglement of two photons in one cavity and zero in another cavity.

We present two schemes for probabilistically teleporting a two-atom entangled state using a three-atom partially entangled state as the quantum channel in cavity QED with the help of separate atomic measurements. The first scheme is only based on the interaction between two driven atoms and a quantized cavity mode in the large detuning limit, so the effects of both cavity decay and the thermal field are eliminated. In the second scheme, it is necessary to introduce an additional resonant cavity besides the thermal cavity to realize the teleportation, and the corresponding success probability is improved.

In this paper, we propose an entanglement concentration protocol for unknown tripartite W class states via the detection of photons which are leaked out from the cavities. In our scheme, the atom-cavity coupling strength is smaller than the cavity decay rate. Hence, the requirement on the quality factor of the cavities is greatly relaxed. The scheme is for nonpost-selection results and the fidelity of the scheme is not affected by the detection inefficiency and atomic decay. All the processes are within the current technologies.

Quantum mechanics allows one to encode the information in the superposition of a quantum state which embodies the nature of quantum nonlocality. Here we propose a realizable physical scheme for a multiparticle quantum dense coding (QDC) between two users in cavity quantum electrodynamics (QED). We also discuss the feasibility of our scheme within current technology.

We study the interaction between a moving four-level rubidium atom and a single mode cavity field in the presence of a nonlinear Kerr-like medium. We derive the basic equations of motion for the atomic system and show that it is exactly solvable in the rotating wave approximation. The momentum increment, the momentum diffusion and the quasi-probability distribution Q-function of this system are studied. We investigate numerically the influence of the Kerr medium on the evolution of the previous statistical properties in the exact resonant and nonresonant cases where the atom is initially in the ground state and the field is in a coherent state. It is found that the Kerr medium has an important effect on their evolutions. Finally, conclusions and discussion are given.

Schemes for the teleporting of the cavity mode state and the unknown atomic state are proposed in cavity quantum electrodynamics (QED) without joint Bell-state measurement (BSM). The presented schemes are implemented with separate atomic measurements instead of any type of joint measurement. The discussion of the scheme indicates that it can be realized by current technologies.

We investigate the entanglement of two two-mode two-photon Jaynes–Cummings models in the presence of phase decoherence. We find an explicit analytical solution of the system and discuss the influence of the phase decoherenc on the entanglement dynamics. Our results shows that the entanglement of the two initially entangled atoms can remain zero for a finite time and revive later. However, if the phase decoherence is taken into accounted, the entanglement cannot revive completely.

In this article, the problem of a double Ξ-type four-level atom interacting with a single-mode cavity field is considered. The considered model describes several distinct configurations of a four-level atom. Also, this model includes the detuning parameters of the atom-field system. We obtain the constants of motion and the wavefunction is derived when the atom is initially prepared in the upper state. We used this model for computing a number of the field aspects for the considered system. As an illustration, the model is used for studying the time evolution of the Mandel Q-parameter, amplitude-squared squeezing phenomenon and Q-function when the input field is considered in a coherent state. The results show that these phenomena are affected by the presence of detuning parameters.

The atomic system on which we focus is a single four-level atom interacting with two-mode cavity fields. We obtain the wavefunction when the atom is initially in an excited state. The result presented in this context is employed to discuss the collapses–revivals phenomenon, the photon statistics and frequency sum squeezing phenomenon. The influence of the detuning on these phenomena are investigated for two four-level atomic systems. We found that the presence of the detuning leads to an increase of the collapse time while the amount of squeezing decreases. Also, the photon statistics is affected by the existence of the detuning parameters where the anti-bunching effect appears.

We propose a one-step cluster state generation scheme via atomic cavity QED. The current scheme is insensitive to the cavity mode thermal state as well as the atomic spontaneous emission since the gate operations are independent of the cavity mode states and laser power is sufficiently weak. In addition, the needed operation is of geometric nature, so it is robust against random operation errors.

We propose a simple scheme for realizing two-qubit logic gate in cavity QED. In our scheme, the quantum controlled-not gate, phase gate and swap gate can be implemented without the ancillary level. The quantum controlled-not gate and phase gate can be realized easily by only one interaction between atoms and a highly detuned cavity mode with the assistance of a strong classical field. Thus, the scheme is insensitive to both the cavity decay and the thermal field.

In this paper, a model describing the interaction of a five-level (⁸⁵Rb) atom with one-mode cavity field including Kerr nonlinearity is discussed. Analytical solution for this model is presented when the atom is initially prepared in its upper state. The obtained results are then employed to examine the dynamical behavior of atomic inversion, field statistics and field squeezing when the input field is initially considered in a coherent state. It is found that the atom-field properties are influenced by the changing of the coupling constants, the detuning parameters and the Kerr medium.

We propose a scheme for concentrating an arbitrary two-particle non-maximally entangled state into a maximally entangled state assisted with three cavities. The scheme involves two interaction–detection cycles and resonant interaction between atom and cavity mode. With the help of the atom trapped in the cavity, the concentration of a two-particle non-maximally entangled state trapped in separate cavities can be realized with a certain probability according to the results of photon detectors. The important feature of our scheme is that we can realize the concentration of an arbitrary two-atom non-maximally entangled state and we do not perform Bell-state measurements.

Across a broad front in physics, an important advance in recent years has been the increasing ability to observe and manipulate the dynamical processes of individual quantum Systems. Within this context, an important physical system has been a single atom strongly coupled to the electromagnetic field of a high-Q cavity within the setting of cavity quantum electrodynamics (cavity QED). Another promising possibility is provided by the cooperative interaction of light with an atomic ensemble for writing and reading single quanta. Here, I present a brief overview of recent advances in the Quantum Optics Group at Caltech related to optical interactions with single photons and atoms and to applications in quantum information science.

By increasing the lifetime of the excited atoms embedded in a solid-state cavity, the field-ionization rate was enhanced approximately three times over that without the cavity effect. The characteristic temperature dependence of the enhanced field-ionization rate suggested the generation process was dissipative quantum tunneling induced by the strong electron-phonon coupling between localized electrons in the excited atoms and the surrounding lattice vibrations of the host in the cavity.