Research

Microwave circuits made of superconducting materials manifest extremely low electrical resistivity at cryogenic temperature, enabling high-quality microwave components like resonators and qubits. We are working on superconducting microwave circuits with various superconducting materials such as aluminum, niobium, niobium nitride, titanium nitride and used them to develop novel hybrid quantum devices by integrating with various nonlinear components like nanomechanical resonators, kinetic inductance nanowires, and low-dimensional materials. Based on such platforms, we are aiming to develop compact, integrated superconducting microwave devices that can provide new functionalities to replace conventional RF components for scalable quantum computing systems. Potential applications include microwave frequency conversion, non-reciprocal routing, amplification, multiplexing/demultiplexing and squeezing. 

Quantum technologies including quantum computing, communication, and sensing require versatile strategies for interfacing quantum states. Utilizing nanoscale vibrations and sounds enables us to achieve this goal with their unique ability to interact with electromagnetic fields of various frequencies (e.g., microwaves and optical light) and a variety of solid-state quantum states (e.g., spins, electrons, and artificial atoms). Furthermore, mechanical and acoustic waves enable compact micro- and nanoscale devices with their short wavelengths 100,000 times smaller than electromagnetic waves and they also present low energy or information propagation loss with high-quality factors (Q>1 million). The goal is to understand fundamental physical phenomena arising from the interactions involving the nanoscale mechanical motions (phonons) and utilize them to develop chip-scale nanomechanical devices for quantum-enabled technologies. 

We are developing a range of passive and active nanophotonic devices based on silicon-on-insulator and thin-film lithium niobate platforms for quantum technologies. A key platform in our research is the silicon optomechanical crystal, which exploits engineered photonic and phononic bandgaps to co-localize optical and mechanical modes. This architecture enables strong optomechanical coupling between telecommunication-band photons and microwave-frequency phonons.

One particularly promising application of this platform is microwave-to-optical quantum transduction, a critical technology for realizing optical quantum networks that interconnect remote superconducting quantum processors. Such transducers can enable coherent links between microwave-domain quantum processors and low-loss optical communication channels.

Recently, we demonstrated millikelvin cryogenic operation of silicon optomechanical crystal devices and successfully characterized photon–phonon transduction in this platform. Building on these results, our next goal is to integrate these optomechanical systems with superconducting quantum circuits to realize coherent qubit–photon transduction.