On-chip microwave-to-optical quantum coherent converter based on a superconducting resonator coupled to an electro-optic microresonator

TLDR

The paper proposes a device architecture for direct quantum electro‑optical conversion of microwave to optical photons. The converter uses a planar superconducting microwave circuit coupled to an integrated electro‑optical whispering‑gallery‑mode microresonator. The authors demonstrate that vacuum coupling rates of 10–100 kHz are attainable, enabling high‑efficiency microwave‑to‑optical conversion at millikelvin temperatures with only ~1 mW optical power and unity cooperativity.

Abstract

We propose a device architecture capable of direct quantum electro-optical conversion of microwave to optical photons. The hybrid system consists of a planar superconducting microwave circuit coupled to an integrated whispering-gallery-mode microresonator made from an electro-optical material. We show that electro-optical (vacuum) coupling rates $g_0$ as large as$\sim 2\pi \, \mathcal{O}(10-100)$ kHz are achievable with currently available technology, due to the small mode volume of the planar microwave resonator. Operating at millikelvin temperatures, such a converter would enable high-efficiency conversion of microwave to optical photons. We analyze the added noise, and show that maximum conversion efficiency is achieved for a multi-photon cooperativity of unity which can be reached with optical power as low as $ \mathcal{O}(1)\,\mathrm{mW} $.