Towards a deterministic interface between trapped-ion qubits and travelling photons

TL;DR

This paper demonstrates a highly efficient, near-ideal quantum interface between a trapped-ion qubit and traveling photons, achieving record photon collection and entanglement probabilities, and showcasing multi-photon generation capabilities.

Contribution

It presents experimental results that reach the theoretical efficiency limits for ion-photon interfaces, advancing the development of deterministic quantum communication systems.

Findings

Single ion-entangled photon probability of 0.69(3)

Photon generation and detection probability of 0.462(3)

Demonstrated generation of 15 sequential polarized photons

Abstract

Experimental results are presented on the efficiency limits for a quantum interface between a matter-based qubit and a photonic qubit. Using a trapped ion in an optical cavity, we obtain a single ion-entangled photon at the cavity output with a probability of 0.69(3). The performance of our system is shown to saturate the upper limit to photon-collection probability from a quantum emitter in a cavity, set by the emitter's electronic structure and by the cavity parameters. The probability for generating and detecting the ion-entangled fiber-coupled photon is 0.462(3), a five-fold increase over the previous best performance. Finally, the generation and detection of up to 15 sequential polarised photons demonstrates the ability of a trapped ion to serve as a multi-photon source. The comparison between measured probabilities and predicted bounds is relevant for quantum emitters beyond trapped ions, in particular, for the design of future systems optimising photon collection from, and absorption in, quantum matter.