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Optics Express

Photon-pair generation from a chip-scale Cs atomic vapor cell

Heewoo Kim, Jiho Park, Hyun-Gue Hong, Taeg Yong Kwon, Jongchenol Park, Han Seb Moon

Published May 11, 2022• 6 citations
Publisher

Abstract

The realization of a narrowband photonic quantum source based on an atomic device is considered essential in the practical development of photonic quantum information science and technology. In this study, we present the first step toward the development of a photon-pair source based on a microfabricated Cs atomic vapor cell. Time-correlated photon pairs from the millimeter-scale Cs vapor cell are emitted via the spontaneous four-wave mixing process of the cascade-type 6S1/2–6P3/2–8S1/2 transition of 133Cs. The maximum normalized cross-correlation value between the signal and idler photons is measured as 622(8) under a weak pump power of 10 µ;W. Our photon source violates the Cauchy–Schwartz inequality by a factor of >105. We believe that our approach has very important applications in the context of realizing practical scalable quantum networks based on atom–photon interactions.

DOI
10.1364/oe.454322

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Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•May 1, 2013•1 citation
The realization of a narrowband photonic quantum source based on an atomic device is considered essential in the practical development of photonic quantum information science and technology. In this study, we present the first step toward the development of a photon-pair source based on a microfabricated Cs atomic vapor cell. Time-correlated photon pairs from the millimeter-scale Cs vapor cell are emitted via the spontaneous four-wave mixing process of the cascade-type 6S1/2–6P3/2–8S1/2 transition of 133Cs. The maximum normalized cross-correlation value between the signal and idler photons is measured as 622(8) under a weak pump power of 10 µ;W. Our photon source violates the Cauchy–Schwartz inequality by a factor of >105. We believe that our approach has very important applications in the context of realizing practical scalable quantum networks based on atom–photon interactions.
Abstract The realization of a narrowband photonic quantum source based on a chip-scale atomic device is considered essential in the practical development of photonic quantum information science and technology. In this study, we present the first step toward the development of a photon-pair source based on a microfabricated chip-scale Cs atomic vapor cell. Time-correlated photon pairs from the millimeter-scale Cs vapor cell are emitted via the spontaneous four-wave mixing process of the cascade-type 6S1/2–6P3/2–8S1/2 transition of 133Cs. The maximum normalized cross-correlation value between the signal and idler photons is measured as 622(8) under a weak pump power of 10 mW. Our photon source violates the Cauchy–Schwartz inequality by a factor of >105. We believe that our approach has very important applications in the context of realizing practical scalable quantum networks based on atom–photon interactions.
Hybrid photonic quantum networks require photonic quantum states generated from different systems, such as atoms and quantum dots. Photonic quantum sources based on atomic ensembles are excellent candidates due to their brightness, low noise, and narrowband characteristics. Herein, a new platform for a highly efficient biphoton source is presented using a thin, dense atomic medium from a hot 1 mm‐long chip‐scale Cs atomic vapor cell. Strongly correlated bright biphotons are generated via spontaneous four‐wave mixing from a dense atomic ensemble based on the 6S1/2–6P3/2–6D5/2 transition of 133Cs. Biphoton source achieves a detected biphoton count rate of 100 kilo‐counts per second, a heralding efficiency of 15%, and a maximum normalized crosscorrelation function value of 100 between the signal and idler photons, despite the low detector efficiency of a silicon avalanche photodetector being less than 25% at 917 nm. Herein, the maximal violation of the Cauchy–Schwarz inequality by a factor greater than 106 at a pump power of 1 μW is obtained. The scheme for a highly efficient photon source is believed to be useful for scalable quantum networks.
Superradiance is one of the most fundamental collective quantum phenomena in light-matter interactions and has been studied extensively since Dicke's seminal work. However, its practical implementation remains challenging because superradiant enhancement requires strict experiment conditions for strong collective coupling among emitters. Can superradiance emerge in a simple platform, such as an atomic vapor cell composed of thermally moving atoms? To address this question, we identify the key signatures of superradiance in a hot atomic ensemble and find a use case of superradiance using an atomic vapor cell. Here, the Photon-Pair SuperRadiance (PPSR) process in an atomic vapor cell provides a novel approach to generating superradiant quantum light from a practical atomic platform. We experimentally demonstrate a superradiant entangled photon-pair generation via PPSR process in a high-density, 1-mm-long chip-scale Cs vapor cell. The hot, dense atomic vapor cell allows the mean interatomic distance in the Doppler-broadened atomic ensemble to be reduced to 0.29 times the idler-photon wavelength, satisfying the condition for cooperative emission. The thin chip-scale geometry enables high atomic densities while mitigating the reabsorption of emitted photons and maintaining moderate optical depth. In this subwavelength regime, we clearly observe the temporal narrowing of the biphoton wavefunction from 0.60 ns to 0.17 ns due to a superradiant decay. This pronounced temporal compression provides strong evidence of collective superradiant emission in the chip-scale Cs vapor cell. Our PPSR source delivers a detected photon-pair rate exceeding 10^6 pairs/s while maintaining a high coincidence-to-accidental ratio of 280.
Generation of nonclassical light is an essential tool for quantum optics research and applications in quantum information technology. We present realization of the source of nonclassically correlated photon pairs based on the process of spontaneous four-wave-mixing in warm atomic vapor. Atoms are excited only by a single laser beam in retro-reflected configuration and narrowband frequency filtering is employed for selection of correlated photon pairs. Nonclassicality of generated light fields is proved by analysis of their statistical properties. Measured parameters of the presented source promise further applicability for efficient interaction with atomic ensembles.
We report on a source of narrowband pairs of time-correlated photons generated via four-wave mixing in a laser-cooled atomic ensemble of87Rb atoms. We employ a cascade decay level scheme in which two copropagating pump beams of 780nm and 776nm excite the atoms to the 5D3/2, F = 3 level and the photon pairs of wavelength 762nm and 795nm from the cascade decay are coupled into single mode fibers and sent to silicon avalanche photodetectors. The photodetection events exhibit a strong correlation in time (g(2)(τ = 0) ≈ 5800), and a high coupling efficiency, as indicated by a pair-to-single ratio of 23%. An instantaneous pair generation rate of 7700 pairs per second (uncompensated for optical losses and detector efficiency) is observed with an increased 776nm pump power of 14mW. The violation of the Cauchy-Schwarz inequality by a factor of 8.4 × 106indicates a strong non-classical correlation between the generated fields, while a Hanbury-Brown-Twiss experiment in the individual photons reveals their thermal nature.