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Communications in Theoretical Physics

Continuous-Variable Entanglement Generation from a Four-State Atom under Raman Excitation

Ting-Ting Zha, Aixi Chen, Wen‐Xing Yang

Published Dec 1, 2011• 1 citation
Publisher

Abstract

We investigate the generation and the evolution of continuous-variable (CV) entanglement from a laser-driven four-state atom inside a doubly resonant cavity under Raman excitation. Two transitions in the four-state atom independently interact with the two cavity modes, while two other transitions are driven by coupling laser fields. By including the atomic relaxation as well as cavity losses, we show that the CV entanglement with large mean number of photons can be generated in our scheme. We also show that the intensity of the coupling laser fields can influence effectively the entanglement period of the cavity field. Different from the conventional resonant excitation scheme where zero one-photon detuning are required, it is found that the intensity and period of entanglement between the two cavity modes as well as the total mean photon number of the cavity field can be adjusted by properly modulating the frequency detuning.

DOI
10.1088/0253-6102/56/6/22

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We propose a scheme for the entanglement generation of two cavity modes using a four-level Raman-driven quantum-beat laser (QBL). The atomic coherence is generated by a Raman-type two-photon process. Two different sufficient conditions for entanglement generation have been investigated. The effect of cavity losses and strength of the driving fields on entanglement generation is studied for different initial states of the resonant cavity modes. The results are in agreement with the earlier scheme for the entanglement generation using a directly driven quantum-beat laser. We observe entanglement generation even for high cavity losses and with low strength of the driving fields. Further, there is no dipole-forbidden transition in the Raman-driven QBL system. Thus the proposed scheme for the entanglement generation is experimentally more viable as compared to the previous directly driven QBL system.
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