Spin-Squeezing Entanglement of Second-Harmonic Generation

Harry J. Kimble, Silvania F. Pereira, Min Xiao

Duger Ulam-Orgikh

Ulrik L. Andersen, Preben Buchhave

We investigate, theoretically, the generation of bright and vacuum-squeezed light as well as entanglement in intracavity, type II, phase-matched second-harmonic generation. The cavity in which the crystal is embedded is resonant at the fundamental frequency but not at the second-harmonic frequency. A simple model for the process using semiclassical theory is derived, and quadrature-squeezing spectra of the involved fundamental fields are deduced. The analysis shows that vacuum squeezing reminiscent of subthreshold optical parametric oscillator squeezing is present and, in the ideal case, perfect. Under slight modifications of the operational conditions, the system is shown to produce efficient bright, squeezed light. Furthermore, we investigate the degree of polarization squeezing and find that three Stokes parameters can be squeezed simultaneously. Finally, we gauge the process for possible entanglement.

نسرین هاشمی دیجوجین, قادر نجارباشی, بهمن سیفی

Coherent and squeezed photon states have attracted a lot attetion in long time ago, since these states can generate in laboratory. These states are satisfying in minimum uncertainty relation. In recently, states have generates with electrons by Bose-Einstein condensations and particles oscillations. Also,this states are satisfying in minimum uncertainty relation, with this difference that parameters in this states are the first and second moments of soin operators instead of position and momentum operators.The similarity phenomenon about squeezing photon is exist for spin with that distance. The source of spin squeezing in multi-qubit states is entanglement. One applecations of spin squeezing is to detect quantum entanglement which plays a key role in both the foundations of quantum physics and quantum computation processing. In recent years, spin squeezing stsate parameters have close relation with entanglement measure, concurrence, that we can characterize entanglement for a class of many-body spin- states. In reality, spin squeezing parameters are witnesse for many bode entanglement. In this paper; we study relation betweenspin squeezed states and entanglement. Then; we stuy the squeezing spin for -mode and -mode entangled coherent states.

Solomon Getahun

In this article, we have analyzed the squeezing and statistical properties of the light generated by the superposition of second harmonic light and degenerate three level squeezed laser beams. We have found that the mean photon number of the superposed light beams to be the sum of the mean photon number of that of the constituent light beams. However, the photon number variance of the superposed light beams does not happen to be the sum of the photon number variances of the separate light beams. On the other hand, the quadrature variance of the superposed light beams is the sum of the individual light beams. Furthermore, we have observed that the degree of squeezing for the superposed light beams is the average of the segregate light beams and the degree of squeezing is approximately 53.95% below the coherent state level. Even though, we have verified that the superposition of subharmonic and second harmonic light with injected degenerate three-level laser beams he haves squeezing, we do not show continuous variable entanglement. But, the absence of the laser beam in the superposition state give rise entangled photons.