A spin-optomechanical quantum interface enabled by an ultrasmall mechanical and optical mode volume cavity

TL;DR

This paper introduces a novel spin-optomechanical quantum interface using a diamond nanobeam cavity with ultra-small mode volumes, enabling high-fidelity entanglement and telecom-compatible quantum communication.

Contribution

It proposes a new diamond nanobeam design with high spin-mechanical coupling and optical efficiency, facilitating quantum repeater architectures without spectral diffusion issues.

Findings

Achieves spin-mechanical coupling rates up to 40 MHz

Demonstrates potential for high-fidelity Bell pair generation

Operates effectively at temperatures up to 40 K

Abstract

We propose a coherent mechanical interface between defect centers in diamond and telecom optical modes. Combining recent developments in spin-mechanical devices and optomechanical crystals, we introduce a 1D diamond nanobeam with embedded mechanical and electric field concentrator with mechanical and optical mode volumes $V_\mathrm{mech}/\Lambda_\mathrm{p}^3\sim 10^{-5}$ and $V_\mathrm{opt}/\lambda^3\sim 10^{-3} $, respectively. By placing a Group IV vacancy in the concentrator we demonstrate exquisitely high spin-mechanical coupling rates approaching 40 MHz, while retaining high acousto-optical couplings. We theoretically show that such a device, used in an entanglement heralding scheme, can provide high-fidelity Bell pairs between quantum repeaters. Using the mechanical interface as an intermediary between the optical and spin subsystems, we are able to directly use telecom optics, bypassing the native wavelength requirements of the spin. As the spin is never optically excited or addressed, we do not suffer from spectral diffusion and can operate at higher temperatures (up to 40 K), limited only by thermal losses. We estimate that based on these metrics, optomechanical devices with high spin-mechanical coupling will be a useful architecture for near-term quantum repeaters.