Free space interference experiments with single photons and single ions

TL;DR

This paper explores free space experiments with single photons and ions to develop efficient quantum interfaces, focusing on strong focusing techniques and probabilistic entanglement generation for quantum networks.

Contribution

It introduces two approaches for ion-photon interfaces in free space, emphasizing high numerical aperture optics to enhance interaction and entanglement.

Findings

Strong focusing increases photon-ion interaction efficiency.

Probabilistic photon measurement can generate ion entanglement.

Higher numerical aperture improves interface performance.

Abstract

Trapped ion crystals have proved to be one of the most viable physical implementations of quantum registers and a promising candidate for a scalable realization of quantum networks. The latter will require the development of an efficient interface between trapped ions and photons. We describe two research directions that are currently investigated to realize such photonic quantum interfaces in free space using high numerical aperture optics. The first approach investigates how strong focusing of light onto a single ion can increase the interaction strength to achieve efficient interaction between a photon and the ion. The second approach uses a probabilistic measurement on scattered photons to generate entanglement between two ions that could be used to distribute information in a quantum network. For both approaches a higher numerical aperture would increase the efficiency of the interface.