A measure of nonclassicality of quantum states based on the negative values of the Wigner function
(WF) of a charge qubit-field system is proposed. It is found that, the negative values of the field WF are
very sensitive to any change in dissipation parameter. The dissipation leads to a long-time death for both
entanglement and nonclassicality, and also the coherence of the cavity state is lost completely.
Some aspects of the irreversible dynamics of a generalized Jaynes–
Cummings model are addressed. By working in the dressed-state
representation, it is possible to split the dynamics of the entanglement
and coherence. The exact solution of the master equation in
the case of a high-Q cavity with atomic decay is found. Effects of
the atomic spontaneous decay on the temporal evolution of partial
entropies of the atom or the field and the total entropy as a quantitative
measure entanglement are elucidated. The degree of entanglement,
through the sum of the negative eigenvalues of the
partially transposed density matrix and the negative mutual information
has been studied and compared with other measures.
An analytical solution is found for the master equation of a system described
by a nonlinear Jaynes–Cummings model, in the presence of nonlinear quantum
dissipation at zero temperature in the large detuning approximation. We study
the influence of nonlinear quantum dissipation on the output entanglement
dynamics of the atom–field system, considering the field to be initially in
SU(1, 1) coherent states. It is found that in the presence of the nonlinear
quantum dissipation, the amplitude of the output entanglement between the
field and the atom decreases with time, however the entanglement between the
field–atom system and the environment increases with time.
Based on the master equation for the density matrix, the dynamics of the entanglement of the three-level atom
interacting with single-mode field in a finite-Q cavity are studied. It was found that the cavity damping leads to
growing entropy and a strong degradation of the entanglement, therefore the coherence loss and entanglement is
very sensitive to any change in the cavity damping parameter.
In this paper, we analytically solve the master equation for Jaynes–Cummings model in the dispersive
regime including phase damping and the field is assumed to be initially in a superposition of coherent states. Using an
established entanglement measure based on the negativity of the eigenvalues of the partially transposed density matrix
we find a very strong sensitivity of the maximally generated entanglement to the amount of phase damping. Qualitatively
this behavior is also reflected in alternative entanglement measures, but the quantitative agreement between different
measures depends on the chosen noise model. The phase decoherence for this model results in monotonic increase in the total entropy while the atomic sub-entropy keeps its periodic behaviour without any effect.
In this article, we investigate the effects of phase damping on the temporal evolution of different
entanglement measurements and the amount of entanglement for the damped Jaynes–Cummings model. The
master equation is solved for any initial state in the two-level atom. Superpositions of two coherent states (
π/2or π out of phase) and their statistical mixture state are taken as initial states when a phase-damped cavity is
taken into account.
A two-mode cavity field coupled to a two-level atom and damped by the environment through a phasedamped
process is considered. For a chosen initial state, the effects of phase damping on the purity loss of
the global system and different bipartite partitions of the system (atom–two modes, mode–(atom–
mode)) through the tangles are considered. In particular, the effect of phase damping on the amount
of entanglement between atom and field is evaluated by the negativity.
atom via intensity-dependent coupling in the off-resonant case has been studied, where the
leakage of photon through the cavity is taken into account. The effects of cavity damping on
the coherence properties of the atom and the field are studied. The amount of entanglement is
compared with the total correlations. It is found that the atom–field system is inhibited from
going into a pure state in the off-resonant case.
CHIN.PHYS.LETT. Vol. 25, No. 7 (2008) 2492
H. A. Hessian∗, A. -B. A. Mohamed
Faculty of Science, Assiut University, Assiut, Egypt
The atomic decay for a two-level atom interacting with a single mode of electromagnetic field is considered. For a
chosen initial state, the exact solution of the master equation is found. Therefore, effect of the atomic damping on
entanglement (purity loss), degree of entanglement by the negativity, mutual information and atomic coherence
through the master equation are studied.