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Optics Express

Non-degenerated nonclassical photon pairs in a hot atomic ensemble

Qunfeng Chen, Bao‐Sen Shi, Min Hua Feng, Yong-Sheng Zhang, Guang‐Can Guo

Published Dec 16, 2008• 35 citations
Publisher

Abstract

We experimentally demonstrate the generation of non-degenerate nonclassical paired photons in a hot atomic ensemble using off-axis four-wave mixing. The time-resolved second-order correlated function between the Stokes photon and the anti-Stokes photon is given. The two-photon correlation between the photons obtained in this experiment is 1.87+/- 0.04, which leads to the violation of Cauchy-Schwarz inequality by a factor of 1.69+/- 0.14.

DOI
10.1364/oe.16.021708

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We experimentally demonstrate the generation of non-degenerate nonclassical paired photons in a hot atomic ensemble using off-axis four-wave mixing. The time-resolved second-order correlated function between the Stokes photon and the anti-Stokes photon is given. The two-photon correlation between the photons obtained in this experiment is 1.87+/- 0.04, which leads to the violation of Cauchy-Schwarz inequality by a factor of 1.69+/- 0.14.
Counter propagated write and read lasers can be used to generate non-classical correlated photon pairs in an atomic ensemble. We experimentally investigate how the detuning of the write laser affects the non-classical correlation function between the Stokes photon and the anti-Stokes photon, which are generated via a spontaneous four-wave mixing process using an off-axis configuration in a cold 85 Rb atomic ensemble. The change of the time-resolved second-order correlated function between the Stokes and anti-Stokes photons is presented. The experimental result suggests that a suitable choice of detuning should be considered in such an experiment.
We experimentally prepare the non-classical correlated photon pairs at the wavelengths of 780 and 776 nm via the cascade transition of 5S 1/2 –5P 3/2 –5D 5/2 in a hot 85 Rb atomic ensemble. By measuring the function of cross-correlation and auto-correlation of photons, a violation of Cauchy—Schwarz inequality by a factor of 283 is obtained, which clearly indicates a strong non-classical correlation between the generated photons. We also find that noise photons scattered from pump lasers have a strong effect on the Cauchy—Schwarz inequality factor by changing the intensity of the pump laser, the experimental results are consistent with the theoretical predictions.
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We report experimental generation of nonclassically correlated photon pairs from collective emission in a room temperature atomic vapor cell. The nonclassical feature of the emission is demonstrated by observing a violation of the Cauchy-Schwarz inequality. Each pair of correlated photons are separated by a controllable time delay up to 2 microseconds. This experiment demonstrates an important step towards the realization of the Duan-Lukin-Cirac-Zoller scheme for scalable long-distance quantum communication.