Pure single photons from a trapped atom source

TL;DR

This paper demonstrates a highly pure, tunable single-photon source using a trapped ion, achieving extremely low multi-photon probability and confirming its suitability for quantum networks.

Contribution

The authors realize a tunable, on-demand single-photon source with unprecedented purity using a trapped ion, advancing quantum communication technology.

Findings

Single-photon rate of 200 kHz achieved

g²(0) value of (1.9 ± 0.2) × 10⁻³ indicating high purity

Output corresponds to ideal attenuated single photons

Abstract

Single atoms or atom-like emitters are the purest source of on-demand single photons, they are intrinsically incapable of multi-photon emission. To demonstrate this degree of purity we have realized a tunable, on-demand source of single photons using a single ion trapped at the common focus of high numerical aperture lenses. Our trapped-ion source produces single-photon pulses at a rate of 200 kHz with g$^2(0) = (1.9 \pm 0.2) \times 10^{-3}$, without any background subtraction. The corresponding residual background is accounted for exclusively by detector dark counts. We further characterize the performance of our source by measuring the violation of a non-Gaussian state witness and show that its output corresponds to ideal attenuated single photons. Combined with current efforts to enhance collection efficiency from single emitters, our results suggest that single trapped ions are not only ideal stationary qubits for quantum information processing, but promising sources of light for scalable optical quantum networks.