Entangled photon pairs, termed as biphotons, have been the benchmark tool for experimental quantum optics. The quantum-network protocols based on photon-atom interfaces have stimulated a great demand for single photons with bandwidth comparable to or narrower than the atomic natural linewidth. In the past decade, laser-cooled atoms have often been used for producing such biphotons, but the apparatus is too large and complicated for engineering. Here we report the generation of subnatural-linewidth (<6 MHz) biphotons from a Doppler-broadened (530 MHz) hot atomic vapour cell. We use on-resonance spontaneous four-wave mixing in a hot paraffin-coated 87 Rb vapour cell at 63 °C to produce biphotons with controllable bandwidth (1.9-3.2 MHz) and coherence time (47-94 ns). Our backward phase-matching scheme with spatially separated optical pumping is the key to suppress uncorrelated photons from resonance fluorescence. The result may lead towards miniature narrowband biphoton sources.
CITATION STYLE
Shu, C., Chen, P., Chow, T. K. A., Zhu, L., Xiao, Y., Loy, M. M. T., & Du, S. (2016). Subnatural-linewidth biphotons from a Doppler-broadened hot atomic vapour cell. Nature Communications, 7. https://doi.org/10.1038/ncomms12783
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