Heterogeneously Integrated Diamond-on-Lithium Niobate Quantum Photonic Platform

TL;DR

This paper presents a heterogeneous integration of diamond and lithium niobate photonic platforms, enabling efficient photon transfer and collection for scalable quantum networks with enhanced nonlinear and electro-optic functionalities.

Contribution

It introduces a novel hybrid diamond-lithium niobate platform with high-Q cavities and low-loss couplers, advancing scalable quantum photonic circuit integration.

Findings

High-Q diamond photonic crystal cavities achieved (Q > 5x10^4)

Efficient low-loss coupling (~1 dB/coupler) demonstrated

Photon collection from silicon vacancies at cryogenic temperatures successfully implemented

Abstract

Diamond photonics has enabled efficient interfaces for quantum memories and is predicted to be a critical component of quantum networks. However, scalable network architectures require spatial, temporal, and spectral control of photons, which relies on nonlinear and electro-optic functionalities that diamond alone cannot provide. Here, we demonstrate heterogeneous integration of a thin-film lithium niobate (TFLN) platform, which has strong chi-2 nonlinearity and electro-optic effects, with thin diamond films. We demonstrate high-Q diamond photonic crystal cavities (Q factors exceeding 5x10^4 at 735 nm) that are lithographically aligned with TFLN photonic backbone and critically coupled to it. This allows us to realize low-loss diamond-TFLN "escalators" (loss ~1 dB/coupler) that support efficient light transfer between them. At cryogenic temperatures (5K), we can collect photons emitted from silicon vacancies (SiVs) embedded within the diamond structure via the TFLN photonic circuit. This approach establishes a scalable route toward integrated photonic circuits for practical quantum networking and other technologies.