A Quantum Repeater Platform based on Single SiV$^-$ Centers in Diamond with Cavity-Assisted, All-Optical Spin Access and Fast Coherent Driving

TL;DR

This paper demonstrates an efficient, stable quantum repeater node using silicon-vacancy centers in diamond coupled to a microcavity, enabling fast optical spin control and high-fidelity spin initialization for quantum networks.

Contribution

It introduces a novel spin-photon interface with silicon-vacancy centers in diamond integrated into a stable microcavity, advancing quantum repeater technology.

Findings

Purcell factors > 1 achieved in liquid helium environment

Coherent optical driving with Rabi frequency of 290 MHz demonstrated

Spin initialization fidelity of 80% within 67 ns achieved

Abstract

Quantum key distribution enables secure communication based on the principles of quantum mechanics. The distance in fiber-based quantum communication is limited to about a hundred kilometers due to signal attenuation. Thus, quantum repeaters are required to establish large-scale quantum networks. Ideal quantum repeater nodes possess a quantum memory which is efficiently connected to photons, the carrier of quantum information. Color centers in diamond and, in particular, the negatively-charged silicon-vacancy centers are promising candidates to establish such nodes. The major obstacle is an inefficient connection between the color centers spin to the Gaussian optics of fiber networks. Here, we present an efficient spin-photon interface. Individual silicon-vacancy centers coupled to the mode of a hemispherical Fabry-P\'erot microcavity show Purcell-factors larger than 1 when operated in a bath of liquid Helium. We demonstrate coherent optical driving with a Rabi frequency of $290\,\mathrm{MHz}$ and all-optical access to the electron spin in strong magnetic fields of up to $3.2\,\mathrm{T}$. Spin initialization within $67\,\mathrm{ns}$ with a fidelity of $80\,\%$ and a lifetime of $350\,\mathrm{ns}$ are reached inside the cavity. The spin-photon interface is passively stable, enabled by placing a color center containing nanodiamond in the hemispherical Fabry-P\'erot mirror structure and by choosing short cavity lengths. Therefore, our demonstration opens the way to realize quantum repeater applications.