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Physics of Particles and Nuclei Letters

EPR light beams and non-Gaussian quantum distributions in the time domain

N. H. Adamyan, Hayk H. Adamyan, Gagik Yu. Kryuchkyan

Published Nov 19, 2009• 0 citations
Publisher

Abstract

We investigate time-dependent properties of Einstein-Podolsky-Rosen (EPR) light beams generated in nondegenerate optical parametric oscillator (NOPO) driven by a sequence of laser pulses with Gaussian time-dependent envelops. The peculiarities of EPR beams are discussed on the base of quadrature squeezing and also in the framework of phase-space Wigner functions for EPR beams which are combined on a half beam splitter. We also investigate the Wigner functions of intensity-correlated twin beams following the conditional photon state-preparation scheme. It is demonstrated that the Wigner functions involve negative values in parts of the phase space for the schemes with one-, two-, and three-photons.

DOI
10.1134/s1547477109070188

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We investigate time-dependent properties of Einstein-Podolsky-Rosen (EPR) light beams generated in nondegenerate optical parametric oscillator (NOPO) driven by a sequence of laser pulses with Gaussian time-dependent envelops. The peculiarities of EPR beams are discussed on the base of quadrature squeezing and also in the framework of phase-space Wigner functions for EPR beams which are combined on a half beam splitter. We also investigate the Wigner functions of intensity-correlated twin beams following the conditional photon state-preparation scheme. It is demonstrated that the Wigner functions involve negative values in parts of the phase space for the schemes with one-, two-, and three-photons.
We investigate time-dependent properties of Einstein-Podolsky-Rosen (EPR) light beams generated in a nondegenerate optical parametric oscillator (NOPO) driven by a sequence of laser pulses with Gaussian time-dependent envelopes. This investigation continues our previous analysis [H. H. Adamyan and G. Yu. Kryuchkyan, Phys. Rev. A 74, 023810 (2006)] and involves problems of two-mode quadrature squeezing as well as intensity-difference squeezing in the time domain. The peculiarities of EPR beams are also discussed in the framework of phase-space quantum distributions. Two kinds of non-Gaussian Wigner functions, for the reduced one-mode state of periodically pulsed NOPO and for EPR beams which are combined on a one-half beam splitter are calculated numerically. We also investigate the Wigner functions of intensity-correlated twin beams following the conditional photon state-preparation scheme. It is demonstrated that the Wigner functions involve negative values in parts of the phase space for the schemes with one, two, and three photons.
We investigate semiclassical dynamics and quantum properties of light beams generated in time-modulated nondegenerate optical parametric oscillator (NOPO). Having in view production of continuous-variable (CV) entangled states of light beams we propose two experimentally feasible schemes of NOPO: (i) driven by continuously modulated pump field; (ii) under action of a periodic sequence of identical laser pulses. It is shown that the time modulation of pump field amplitude essentially improves the degree of CV entanglement in NOPO. On the whole the level of integral two-mode squeezing, which characterizes the degree of CV entanglement, goes below the standard limit established in an ordinary NOPO with monochromatic pumping. We develop semiclassical and quantum theories of these devices for both below- and above-threshold regimes of generation. Properties of CV entanglement for various operational regimes of the devices are discussed in the time domain in application to time-resolved quantum information technologies. Our analytical results are in well agreement with the results of numerical simulation and support a concept of CV entangled states of time-modulated light beams.
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We investigate quantum properties of phase-locked light beams generated in a nondegenerate optical parametric oscillator (NOPO) with an intracavity waveplate. This investigation continues our previous analysis presented in Phys. Rev. A 69, 053814 (2004), and involves problems of continuous-variable quadrature entanglement in the spectral domain, photon-number correlations as well as the signatures of phase-locking in the Wigner function. We study the role of phase-localizing processes on the quantum correlation effects. The peculiarities of phase-locked NOPO in the self-pulsing instability operational regime are also cleared up. The results are obtained in the PPP-representation as a quantum-mechanical calculation in the framework of stochastic equations of motion, as well as by numerical simulation based on the method of quantum state diffusion.
The solution of the time-dependent periodic pumping non-degenerate optical parametric amplifier (NOPA) is derived when the pump depletion is considered both above and below thresholds. Based on this solution, the quantum fluctuation calculated shows that a high entanglement and a good squeezing degree of the parametric light beams are achieved near and above thresholds. We adopt two kinds of pump fields: (i) a continuously modulated pump with a sinusoidal envelope; (ii) a sequence of laser pulses with Gaussian envelopes. We analyse the time evolution of continuous variable entanglement by analytical and numerical calculations, and show that the periodic driven pumping also improves the degree of entanglement. The squeezing and Einstein–Podolsky–Rosen (EPR) entanglement by using the two pumping driven functions are investigated from below to above the threshold regions, the tendencies are nearly the same, and the Gaussian driven function is superior to that of the sine driven function, when the maximum squeezing and the minimum variance of quantum fluctuation are considered. In the meantime, the generalization of frequency degenerate OPA to frequency non-degenerated OPA problem is investigated.