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arXiv:quant-ph/0703084

Phase Controlled Continuously Entangled Two-Photon Laser with Double ΛΛΛ Scheme

C. H. Raymond Ooi

Published Mar 10, 2007• 0 citations
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Abstract

We show that an absolute coherent phase of a laser can be used to manipulate the entanglement of photon pairs of two-photon laser. Our focus is on the generation of a continuous source of entangled photon pairs in the double $Λ$ (or Raman) scheme. We study the dependence of steady state entanglement on the phase and laser parameters. We obtain a relationship between entanglement and two-photon correlation. We derive conditions that give steady state entanglement for the Raman-EIT scheme and use it to identify region of steady state macroscopic entanglement. No entanglement is found for the double resonant Raman scheme for any laser parameters.

DOI
10.48550/arxiv.quant-ph/0703084

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We show that an absolute coherent phase of a laser can be used to manipulate the entanglement of photon pairs of two-photon laser. Our focus is on the generation of a continuous source of entangled photon pairs in the double ΛΛΛ (or Raman) scheme. We study the dependence of steady state entanglement on the phase and laser parameters. We obtain a relationship between entanglement and two-photon correlation. We derive conditions that give steady state entanglement for the Raman-EIT scheme and use it to identify region of steady state macroscopic entanglement. No entanglement is found for the double resonant Raman scheme for any laser parameters.
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.
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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.
The quantum statistical properties of light emitted by a two-photon double Raman laser is investigated. Using the master equation derived in the good-cavity limit, we study the squeezing and entanglement properties of the cavity field. It turns out that the cavity radiation exhibits two-mode squeezing and entanglement in the transient as well as steady state regime for realizable parameters. We establish a connection between two-mode squeezing and entanglement that gives insight into the physical origin of these quantum features. We also discuss the interplay between the laser detuning and amplitude in modifying the properties of the cavity field.
We show that steady-state entanglement in open quantum systems is controlled by the phase reference of a phase-sensitive reservoir. Using a covariance-matrix approach for Gaussian-preserving dynamics, we demonstrate that purely local, phase-sensitive dissipation can generate entanglement when combined with coherent coupling. The steady state exhibits a finite entangled region with an optimal squeezing strength that maximizes both the magnitude and thermal robustness of entanglement. We find that coherent coupling does not enhance entanglement monotonically, but instead regulates the conversion of local squeezing into nonlocal correlations. Importantly, the coupling dependence is controlled by the phase reference of the squeezed reservoir: phase-locked (rotating-frame) and laboratory-frame implementations yield qualitatively distinct steady states and entanglement structure. These results establish phase-sensitive reservoir engineering as a controllable route to steady-state entanglement in continuous-variable systems. Steady-state entanglement in phase-sensitive open systems depends explicitly on the reservoir phase reference and is not invariant under changes of that reference.}