Atoms in a Cavity: A Source of Narrowband Photon Pairs

Bharath Srivathsan, Gurpreet Kaur Gulati, Mei Yuen Brenda Chng +3 more

S. Haroche

Joanna A. Zielińska, Federica A. Beduini, Morgan W. Mitchell

We present a novel method of generating narrowband atom-resonant photon pairs with a cavity-enhanced SPDC source. Using a Faraday Anomalous Dispersion Optical Filter, we select only a cavity mode containing identical pairs, which we demonstrate by measuring statistical properties of output photons.

Peng Zhou, S. Swain, Gao‐xiang Li +1 more

James K. Thompson, Jonathan Simon, Huanqian Loh +1 more

We generated narrowband pairs of nearly identical photons at a rate of 5 x 10(4) pairs per second from a laser-cooled atomic ensemble inside an optical cavity. A two-photon interference experiment demonstrated that the photons could be made 90% indistinguishable, a key requirement for quantum information-processing protocols. Used as a conditional single-photon source, the system operated near the fundamental limits on recovery efficiency (57%), Fourier transform-limited bandwidth, and pair-generation-rate-limited suppression of two-photon events (factor of 33 below the Poisson limit). Each photon had a spectral width of 1.1 megahertz, ideal for interacting with atomic ensembles that form the basis of proposed quantum memories and logic.

M. Gao, Yin‐Hai Li, Yan Li +4 more

A high-quality narrowband polarization-entangled source in the telecom band is preferred to avoid frequency dispersion for long-distance transmission in optical fibers and to efficiently couple with telecom-band quantum memories. Here, we report narrowband, telecom-band, polarization-entangled photon pair generation based on the superposition of single-longitudinal-mode photon pairs from two monolithic nonlinear crystal cavities in a passively stable interferometer based on beam displacers. The photon pairs generated from the cavities exhibit a high coincidence to accidental coincidence ratio of 20 000 and a bandwidth below 500 MHz. Two-photon polarization interference, Bell inequality, and quantum state tomography are performed to indicate the high quality of the entangled source. The current configuration demonstrates greater stability than traditional free space cavity-enhanced polarization-entangled state generation, which is promising for quantum communication applications.