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Physical Review A

Entanglement in a bright light source via Raman-driven coherence

Sajid Qamar, M. Al-Amri, Muhammad Suhail Zubairy

Published Jan 30, 2009• 35 citations
Publisher

Abstract

We propose a two-photon correlated emission laser to generate entanglement amplifier for bright light source. The coherence between upper and lower levels is generated in a Raman-driven scheme using two external classical fields. The proposed scheme is practically more suitable for the macroscopic entanglement of photons of the two modes of the cavity field.

DOI
10.1103/physreva.79.013831

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We propose a two-photon correlated emission laser to generate entanglement amplifier for bright light source. The coherence between upper and lower levels is generated in a Raman-driven scheme using two external classical fields. The proposed scheme is practically more suitable for the macroscopic entanglement of photons of the two modes of the cavity field.
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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We show that an absolute coherent phase of a laser can be used to manipulate the entanglement of photon pairs in two-photon laser. We present simple physics behind a general master equation for two-photon laser. Our focus is on the generation of a continuous source of macroscopically entangled photon pairs in the double $\ensuremath{\Lambda}$ (or Raman) scheme. We show how the steady-state photon numbers and entanglement depend on the laser parameters, especially the phase. We obtain a relationship between entanglement and two-photon correlation. We derive conditions that give steady-state entanglement for the spontaneous Raman-electromagnetic-induced transparency scheme and use it to identify the region with macroscopic entanglement. No entanglement is found for the double resonant Raman scheme.
We propose a scheme for the entanglement generation of two micromechanical mirrors through two-mode fields generated by a correlated emission laser source in a doubly resonant cavity. The coherence between upper and lower levels is generated in a cascade-driven scheme using two external classical fields. Two input laser fields are both tuned at the Stokes sidebands such that cooling and entanglement of micromechanical mirrors are realizable. We investigate two different conditions for entanglement generation. We show controllable entanglement of both two-mode fields and two mirrors in the steady state. The proposed scheme for the macroscopic entanglement generation is robust against environmental thermalization and in favor of a large cavity dissipation rate.