Microwave to optical transduction with Piezo-Optomechanics utilizing Brillouin Scattering*

At cryogenic temperatures, bulk acoustic resonators support robust, long-lived mechanical modes, capable of coupling to various quantum systems. In separate works, bulk acoustic devices have achieved strong coupling to both superconducting qubits and optical cavities, making it a potential quantum resource.

Here, we combine resonantly-enhanced piezoelectric coupling and Brillouin optomechanical interaction to demonstrate the first Brillouin-based electro-optomechanical system with bulk crystal, enabling new opportunities for spectroscopy and transduction. In particular, we present its capability as a bi-directional quantum transducer.

In this system, we achieve fully resonant and well-mode-matched interactions between a 3D microwave cavity, a high-frequency bulk acoustic resonator, and a Fabry Perot cavity through its modular and highly tunable design. As a result, the system reaches large optomechanical cooperativities (>1), and efficient optical/microwave coupling efficiencies (~0.5), partially satisfying the requirements of an efficient transducer. In this context, we demonstrate piezo-optomechanical transduction efficiency comparable to existing platforms. The system has much room for optimization, leading to a realistic path toward unity conversion. We show preliminary attempts towards system optimization, hinting at the ability to perform optical high power (mW) continuous-wave measurement in our cryogenic superconducting system.