In (Xu and Kuang 2006 J. Phys. A: Math. Gen. 39 L191 ), the authors claim that, for single-mode excited entangled coherent states |Ψ ± (α, m )⟩, 'the photon excitations lead to the decrease of the concurrence in the strong field regime of |α| 2 and the concurrence tends to zero when |α| 2 → ∞ '. This is wrong.
This paper introduces two types of two-mode excited entangled coherent states (TMEECSs) |Ψ±(α, m , n )⟩, studies their entanglement characteristics, and investigates the influence of photon excitations on quantum entanglement. It shows that for the state |Ψ+(α, m , m )⟩ the two-mode photon excitations affect seriously entanglement character while the state |Ψ-(α, m , m )⟩ is always a maximally entangled state, and shows how such states can be produced by using cavity quantum electrodynamics and quantum measurements. It finds that the entanglement amount of the TMEECSs is larger than that of the single-mode excited entangled coherent states with the same photon excitation number.
We study entanglement created between two isolated qubits by interaction with entangled-photon pairs obtained by parametric down-conversion of a laser pump field. The induced entanglement is quantified using the mixed state Concurrence proposed by Wootters et al. [Phys. Rev. Lett. 78, 5022 (1997)]. A universal value of qubit-entanglement, which is independent on the photon-pair wavefunction is identified to leading order in the qubit–field interaction and the pump field amplitude. The qubit entanglement decreases at higher laser pump intensities due to interference between the entangled photon pairs, which creates excitations in the qubit system. Maximal Concurrence is produced by only generating coherences between the ground and the highest excited qubit states.
We introduce a new kind of continuous-variable-type entangled pure states, called single-mode excited entangled coherent states (SMEECSs), which are obtained through actions of a creation operator of a single-mode optical field on the ECSs. We study the mathematical properties and entanglement characteristics of the SMEECSs, and investigate the influence of photon excitations on quantum entanglement. It is shown that the SMEECSs form a type of cyclic representation of the Heisenberg–Weyl algebra. It is found that the photon excitations seriously affect the entanglement character of the SMEECSs. We also show how such states can be produced by using cavity QED and quantum measurements.
An entangled quantum state is considered by applying a local photon excitation to each mode of an entangled coherent state.The entanglement property is investigated in terms of the entropy of entanglement.It is shown that applying a photon addition can improve the amount of entanglement.It is also examined that in a specific region of parameters, the state |ψ - 1 (α, m, n) is least entangled when photon excitation is minimum.We study the statistical properties of such states by employing the quasi-probability functions.
In this paper, after a brief review of the single-mode excited entangled coherent states, two new classes of continuous-variable entangled pure states, namely, single-mode nonlinear excited entangled coherent states, have been produced by using the f -deformed creation operator instead of . In order to establish the nonclassicality of the states, some of the physical properties of the corresponding entangled states, such as entanglement degree, photon statistics, second-order correlation function and quadrature squeezing have been studied in detail by choosing a particular f -deformation function. In addition, the influence of photon excitations on the properties of our introduced states has been analyzed and the results compared with those of a single-mode excited entangled coherent state. In continuation, a theoretical scheme for their generation based on the interaction of a two-level atom with a quantized cavity field has been proposed.