Abstract
Quantum information technology strongly relies on coupling of optical photons with narrowband quantum systems, such as quantum dots, color centers, and atomic systems. This coupling requires matching the optical wavelength and bandwidth to the desired system, which presents a considerable problem for most available sources of quantum light. Here we demonstrate coupling of alkali dipole transitions with a tunable source of photon pairs. Our source is based on spontaneous parametric down-conversion in a triply-resonant whispering-gallery mode resonator. For this, we have developed novel wavelength tuning mechanisms, which allow for a coarse tuning to either cesium or rubidium wavelength with subsequent continuous fine-tuning to the desired transition. As a demonstration of the functionality of the source, we performed a heralded single photon measurement of the atomic decay. We present a major advance in controlling the spontaneous down-conversion process, which makes our bright source of single photons now compatible with a plethora of narrow-band resonant systems.
Highlights
Photon pairs and heralded single photons are key prerequisites for many schemes in quantum information processing [1,2]
We reported a source based on spontaneous parametric downconversion (SPDC) in an optical resonator operating in a single-mode regime [13], and providing tunable bandwidth [14] compatible with atomic transitions
We have demonstrated tunable and efficient interaction of two narrowband atomic resonances with photons created via SPDC in a whispering gallery mode resonator (WGMR)
Summary
Photon pairs and heralded single photons are key prerequisites for many schemes in quantum information processing [1,2] Making their central frequency and bandwidth compatible to the resonances of other physical systems enables a variety of applications, such as efficient quantum memories [3,4], photon–phonon interactions [5], and coupling single photons or squeezed light with single atoms [6] or atomic ensembles [7,8]. We show continuous tuning of the signal frequency across the Dopplerbroadened absorption line of a Cs D1 hyperfine transition by manipulating the evanescent fields of the pump, signal, and idler with a movable dielectric substrate This continuous frequency tuning with MHz precision allows heralded single-photon spectroscopy, which we demonstrate at this Cs D1 hyperfine transition
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