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Physical Review A

Continuous-variable entanglement in a nondegenerate three-level laser with a parametric oscillator

Eyob Alebachew

Published Aug 13, 2007• 59 citations
Publisher

Abstract

We consider a nondegenerate three-level cascade laser with a subthreshold nondegenerate parametric oscillator coupled to a vacuum reservoir. Applying the pertinent master equation, we analyze the squeezing and entanglement properties of the two-mode light produced by this quantum optical system inside and outside the cavity. We also determine the normalized second-order correlation function for the two-mode light as well as for individual mode. We find that the light generated by this system is in a two-mode squeezed state and the state of the system is strongly entangled at steady state. Moreover, the presence of the parametric oscillator leads to an increase in the degree of squeezing and entanglement. We also find that the intermode correlation decreases as the injected atomic coherence decreases in the system.

DOI
10.1103/physreva.76.023808

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We consider a nondegenerate three-level cascade laser with a subthreshold nondegenerate parametric oscillator coupled to a vacuum reservoir. Applying the pertinent master equation, we analyze the squeezing and entanglement properties of the two-mode light produced by this quantum optical system inside and outside the cavity. We also determine the normalized second-order correlation function for the two-mode light as well as for individual mode. We find that the light generated by this system is in a two-mode squeezed state and the state of the system is strongly entangled at steady state. Moreover, the presence of the parametric oscillator leads to an increase in the degree of squeezing and entanglement. We also find that the intermode correlation decreases as the injected atomic coherence decreases in the system.
The quantum properties of a nondegenerate three-level cascade laser coupled to a two-mode vacuum reservoir are throughly analyzed with the use of the pertinent master equation and stochastic differential equations associated with the normal ordering. Particularly, the enhancement of squeezing and the amplification of photon entanglement of the two-mode cavity light are investigated. It is found that the two cavity modes are strongly entangled, and the degree of entanglement is directly related to the two-mode squeezing. Moreover, the squeezing and entanglement of the cavity radiation enhance with the rate of atomic injection.
Squeezing and entanglement of a two-mode cascade laser, produced by a three-level atom which is initially prepared by a coherent superposition of the top and bottom levels then injected into a cavity coupled to a two-mode squeezed vacuum reservoir is discussed. I obtain stochastic differential equations associated with the normal ordering using the pertinent master equation. Making use of the solutions of the resulting differential equations, we determined the mean photon number for the cavity mode and their correlation, EPR variables, smallest eigenvalue of the symplectic matrix, intensity difference fluctuation, and photon number correlation. It is found that the squeezed vacuum reservoir increases the degree of the statistical and nonclassical features of light produced by the system. Furthermore, using the criteria developed by logarithm negativity and Hillery-Zubairy criteria, the quantum entanglement of the cavity mode is quantified. It is found that the degree of the entanglement for the system under consideration increases with the squeezing parameter of the squeezed vacuum reservoir.
We consider a two-mode light generated by nondegenerate three-level laser with parametric oscillator in optomechanical cavity coupled to two-mode squeezed vacuum reservoir. Effects of pump mode, optomechanical coupling strength and squeezed vacuum reservoir on squeezing and entanglement properties of the cavity modes have been analyzed using the expectation values of cavity mode variables at steady state. The results show that the two-mode light produced by the system under consideration exhibits quadrature squeezing and entanglement. The presence of parametric oscillator in the cavity and squeezed vacuum reservoir enhance the degree of squeezing, entanglement and mean photon number of the cavity mode lights. The optomechanical cavity has no effect on the mean photon number and entanglement of the cavity mode but increases the degree of quadrature squeezing.
We consider a three-level cascade laser in which a coherently driven non-degenerate three-level atom available in a closed cavity coupled to a twomode vacuum reservoir.Applying the interaction Hamiltonian and Heisenberg equation of motion, we analyze the mean photon number, quadrature squeezing, and entanglement properties of the light produced by this quantum optical system inside the cavity.We find that the light generated by this system is in a two-mode squeezed state under certain conditions and the state of the system is weakly entangled at steady state due to the presence of the two-mode vacuum reservoir noise.
We study a nondegenerate three-level cascade laser coupled to a two-mode vacuum reservoir, by employing the stochastic differential equations associated with the normal ordering. The amplification of the properties of squeezing and entanglement of the cavity light is investigated. We have found that there is an entanglement between the states of the light generated in the cavity, due to the strong correlation of the light emitted, when the atom decays from the top level to the bottom level via the intermediate one. We have also obtained that the two cavity modes are strongly entangled, and the degree of entanglement is directly related to the two-mode squeezing.