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arXiv:quant-ph/0607153 · Physical Review A

Role of the Bell singlet state in the suppression of disentanglement

Ru-Fen Liu, Chia-Chu Chen

Published Aug 29, 2006• 43 citations
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Abstract

The stability of entanglement of two atoms in a cavity is analyzed in this work. By studying the general Werner states, we clarify the role of Bell singlet state in the problem of suppression of disentanglement due to spontaneous emission. It is also shown explicitly that the final amount of entanglement depends on the initial ingredients of the Bell singlet state.

DOI
10.1103/physreva.74.024102

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The stability of entanglement of two atoms in a cavity is analyzed in this work. By studying the general Werner states, we clarify the role of Bell singlet state in the problem of suppression of disentanglement due to spontaneous emission. It is also shown explicitly that the final amount of entanglement depends on the initial ingredients of the Bell singlet state.
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We analyse the influence of entanglement on the emission properties of atoms. To this end, first, we propose a scheme for the preparation of a pair of entangled Helium atoms, one in the ortho and the other in the para spin configuration. We discuss a realistic scenario for this process, based in the double ionization of He by intense laser fields. These states are used to analyse disentanglement and the role of entanglement in the spontaneous emission from the pair. In particular, we show that the decaying rate of an entangled atom is different from that in a product state, modifying the temporal emission distribution and lifetime of the atoms.
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Decoherence effect on quantum entanglement of two optical qubits in a lossy cavity interacting with a nonlinear medium (Kerr nonlinearity) is analyzed. The qubits are assumed to be initially in the maximally entangled states (Bell or Bell-like states) or the maximally entangled mixed states, on the example of Werner and Werner-like states. Two kinds of measures of the entanglement are considered: the concurrence to describe a decay of the entanglement of formation of the qubits, and the negativity to determine a decay of an upper bound of the entanglement of distillation. It is observed that the Kerr nonlinearity does not affect the entanglement of the qubits initially in the Bell or Werner states, although the evolution of the qubits can depend on this nonlinearity explicitly. However, it is shown that for the initial Bell-like state and the corresponding Werner-like state, the loss of entanglement can be periodically reduced by inserting the Kerr nonlinearity in the lossy cavity.