Two-Photon Interference of Photons from Remote Tin-Vacancy Centers in Diamond

TL;DR

This paper demonstrates two-photon interference between remote tin-vacancy centers in diamond, showing high interference visibility and tunability, advancing the development of scalable quantum networks using solid-state qubits.

Contribution

It presents the first remote two-node interference experiment with tin-vacancy centers, including frequency tuning via the Stark effect to achieve high-visibility interference.

Findings

Achieved up to 80% interference visibility without postprocessing.

Demonstrated 4 GHz Stark tuning while maintaining optical coherence.

Maintained 63% interference visibility with detuning up to 20 times the natural linewidth.

Abstract

Scalable quantum networks rely on optical connections between long-lived qubits to distribute entanglement. Tin vacancies in diamond have emerged as promising long-lived qubits, offering extended spin coherence times at liquid helium temperatures and spin-dependent, highly coherent optical transitions for effective photon-based communication. Connecting remote nodes requires quantum interference of indistinguishable photons, which is challenging in an inhomogeneous solid-state environment. Here, we demonstrate a two-node experiment with tin vacancies in diamond, which exhibit a resonant frequency distribution spanning approximately 8 GHz. To overcome the frequency mismatch, we tune the resonant frequencies of one node using the Stark effect. We achieve tunability up to 4 GHz while maintaining optical coherence. As a demonstration, we achieve detuning-dependent remote two-photon interference between separate nodes, obtaining 80(6)% interference visibility without postprocessing when the defects' optical transitions are tuned into resonance, and 63(8)% with detuning up to 20 times their natural linewidths. These results highlight the potential of tin-vacancy centres in diamond for establishing robust optical links between remote quantum registers.