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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

Entanglement of a one-atom dressed-state laser

Xiu Zhang

Published Nov 19, 2011• 0 citations
Publisher

Abstract

We shown that it is possible to produce a entangled one-atom dressed-state laser via atomic coherence effcets. For a V-type three-level atom embedded in a two-mode cavity, two applied fields induce a quantum-beat and the collective field comes into interaction. The stastics of the collective field is sub-Poissonian in the good cavity condition. The collective field intensity quantum noise reducetion produces the entanglement between two cavity fields.

DOI
10.1117/12.918111

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We shown that it is possible to produce a entangled one-atom dressed-state laser via atomic coherence effcets. For a V-type three-level atom embedded in a two-mode cavity, two applied fields induce a quantum-beat and the collective field comes into interaction. The stastics of the collective field is sub-Poissonian in the good cavity condition. The collective field intensity quantum noise reducetion produces the entanglement between two cavity fields.
We explore the quantum entanglement between two collective fields via atomic coherence effects. For three-level atoms in V\mathsf{V}V configuration driven by two applied fields on two-photon resonance, one coherent superposition of the excited states is not excited, which is the counterpart of coherent population trapping. The coherence-induced depopulation makes two cavity fields in each collection combine into a quantum-beat, i.e., equivalently, the difference mode of the two components decouples from the driven atoms. The two sum modes, when they are arranged in the four-wave mixinglike interactions, can be prepared in Einstein-Podolsky-Rosen entangled state. Correspondingly, any two individual fields from different collective modes are entangled with each other. Furthermore, the effects of thermal reservoir and laser linewidths are discussed, and a generalization is given to the case in which each quantum beat involves more than two modes.
We show that it is possible to achieve laser oscillation and two-mode entanglement by using dressed-state phase-dependent electromagnetically induced transparency (EIT) in a double $\ensuremath{\Lambda}$ system. Under certain conditions, two beams of bichromatic fields induce the depopulation of a coherent superposition state of the two excited states and the quantum beat of a pair of cavity fields. While one of two beams of bichromatic fields dresses the atoms, the other and the pair of cavity fields are in phase-controlled EIT interaction with the dressed atoms. On the basis of this, the pair of cavity fields not only operates well above threshold and exhibit subshot noise but also is in an entangled state. This mechanism suggests an efficient way to achieve bright entangled source of light.
We examine the quantum correlations at steady state in a three-mode quantum-beat laser that operates well above threshold. The analysis is presented by employing the dressed-atom combination-mode picture, in which only one combination mode of three cavity fields is coupled to the active medium, while the other two combination modes are decoupled. For suitable operating conditions, the coupled mode has the intensity fluctuations below the shot noise, while the two decoupled modes retain in their vacuum states. This determines that all of the original modes exhibit sub-Poissonian statistics. When the system operates well above threshold, the van Loock-Furusawa inequality is satisfied, concluding that the genuine tripartite entanglement among three sub-Poissonian fields is established. Physically, the responsible mechanism is the combined effect of atomic coherence controlled correlated-spontaneous emission and intrinsic feedback.
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