Effects of frequency detuning and excitation quantum number on the dynamics of entanglement in the Jaynes-Cummings polariton model

We present a scheme for generating polaritons which are maximally entangled qubit states in the Jaynes-Cummings interaction mechanism. Considering a specific case of an atom initially in an excited state entering a cavity mode initially in vacuum state and in a non-resonant atom-field Jaynes-Cummings interaction, we demonstrate using graphical representation on the Bloch sphere that an increase in frequency detuning leads to an increase in Rabi oscillations. Analysis of the dynamical behaviour of quantum entanglement in the general Jaynes-Cummings atom-field interactions measured by concurrence show that frequency detuning and photon number parameters are vital in enhancing entanglement.

Dynamics of entanglement of atoms with two-photon transitions induced by a thermal field

In this paper, we investigate the entanglement between two two-level atoms non-resonantly in-teracting with a thermal field of a lossless one-mode resonator via degenerate two-photon transi-tions. On the basis of the exact solution of the time-dependent density matrix we calculate the negativity as a measure of atomic entanglement. We show that for separable initial atomic states a slight atom-field detuning may generate the high amount of atom-atom entanglement. The re-sults also show that for non-resonant atom-field interaction the entanglement induced by nonlin-ear two-photon interaction is smaller than that induced by one-photon interaction in contrast to the resonant interaction situation. For a Bell-type entangled initial atomic state we obtain that if the detuning increases, there is an appreciable decrease in the amplitudes of the negativity oscilla-tions. The results also show that elimination of the sudden death of entanglement for non-resonant two-photon atom-field interaction may take place.

ENTANGLEMENT PREPARATION AND QUANTUM INFORMATION PROCESSING WITH ATOMS TRAPPED IN SEPARATED CAVITIES THROUGH A SINGLE RESONANT ATOM–FIELD INTERACTION

In this paper, a scheme is presented for generation of W-type entangled states for n atoms trapped in separated cavities connected by optical fibers. The scheme only requires a single atom–cavity–fiber interaction and no classical field is needed. Due to these features, the scheme is simpler and more robust against decoherence than the previous ones. The scheme can also be used to realize quantum state transfer and controlled phase gates between qubits located at distant nodes of a quantum network.

Entanglement transfer between atomic qubits and thermal fields

We investigate entanglement reciprocation between atomic qubits and cavity fields initially in a thermal state. We show that the entanglement between the atomic qubits can be fully transferred to the mixed fields through displacement operation and resonant atom-cavity interaction. This is a rare example, in which quantum systems in mixed states can be used as the memory for entanglement. The entanglement can be retrieved by another atomic pair. Apart from fundamental interest, the results are useful for implementation of quantum networking with atom-field interface in the microwave regime.