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Stabilized Fabry-Perot Filters for Enhancing Nonclassical Correlations of Light Scattered by an Ensemble of Cold Two-Level Atoms

A. A. C. de Almeida, Lucas S. Marinho, W. Martins, G. C. Borges, D. Felinto

Published Jan 1, 2024• 0 citations
Publisher

Abstract

We present a design of an actively stabilized Fabry-Perot cavity to filter the biphotons generated via spontaneous four-wave mixing in cold two-level atoms. Preliminary results show that quantum correlations are enhanced within the filtered signal.
DOI
10.1364/cleo_at.2024.jw2a.119

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We report the enhancement of quantum correlations for biphotons generated via spontaneous four-wave mixing in an ensemble of cold two-level atoms. This enhancement is based on the filtering of the Rayleigh linear component of the spectrum of the two emitted photons, favoring the quantum-correlated sidebands reaching the detectors. We provide direct measurements of the unfiltered spectrum presenting its usual triplet structure, with Rayleigh central components accompanied by two peaks symmetrically located at the detuning of the excitation laser with respect to the atomic resonance. The filtering of the central component results in a violation of the Cauchy-Schwarz inequality to (4.8±1.0)≰1 for a detuning of 60 times the atomic linewidth, representing an enhancement by a factor of four compared with the unfiltered quantum correlations observed at the same conditions.
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The nonclassical photon pair, generated via a parametric process, is naturally endowed with a specific form of frequency-time quantum correlations. Here, we report complete control of frequency-time quantum correlations of narrow-band biphotons generated via spontaneous four-wave mixing in a cold atomic ensemble. We have experimentally confirmed the generation of frequency-anticorrelated, frequency-correlated, and frequency-uncorrelated narrow-band biphoton states, as well as verifying the strong nonclassicality of the correlations. Our work opens up new possibilities for engineering narrow-band entangled photons for various quantum optical and quantum information applications.