Generation of narrow-bandwidth paired photons with electronically controllable waveforms

Chinmay Belthangady, Shengwang Du, Stephen E. Harris +2 more

Vlatko Balić, Danielle Braje, Pavel Kolchin +2 more

This study reports the experimental demonstration of a high-brightness source of paired photons based on an double-/spl Lambda/ atomic level configuration in cold /sup 87/Rb atoms. The source is capable of producing pairs of correlated photons with bandwidths as small as 5 MHz at into a single spatial mode. Strong counter-propagating coupling and pump lasers are applied and the system spontaneously emits pairs of photons at Stokes and anti-Stokes frequencies. The backward-wave geometry ensures that a spontaneously emitted photons will be oppositely directed and that they can be detected without additional filtering.

Danielle Braje

Luwei Zhao, Xianxin Guo, Chang Liu +3 more

The generation of nonclassical photon pairs with a long coherence time is key for applications that range from fundamental to quantum communication and metrology. Spontaneous four-wave mixing with electromagnetically induced transparency has been demonstrated as one of the most efficient methods; however, narrowing the bandwidth and producing photon pairs with a temporal length beyond 1 μs remains a technical challenge due to noise considerations and the need for cold atoms with a high optical depth (OD). In this work, we demonstrate the generation of narrowband photon pairs with a controllable coherence time up to 1.72 μs in a laser-cooled atomic ensemble with an OD as high as 130. At such a high OD, we find that the pump laser field spatial profile has a significant effect on the time–frequency entangled two-photon waveform. We also confirm the quantum particle nature of heralded narrowband single photons generated from this source.

J. F. Chen, Shengwang Du

In this article, we review on narrowband photon pairs produced in nonlinear crystals, and especially in atomic ensembles. In atomic ensembles, “write-read” process in pulse mode and spontaneous four-wave mixing process (SFWM) in continuous mode are two popular photon pair generation schemes. We specifically discuss the experimental works with continuous SFWM scheme in cold atomic ensembles. Photon pairs produced in these systems are characteristic of controllable long coherence time, and therefore are accessible with direct temporal modulation. We elaborate on the recent techniques on modulation and waveform reshaping of narrow-band paired photons.

Shengwang Du