Paul Burger, Quantum Technology

Main supervisor: Raphaël Van Laer, Assistant Professor, Quantum Technology 
Assist Supervisor: Dag Winkler, Professor, Quantum Device Physics
Examiner: Simone Gasparinetti, Associate Professor, Quantum Technology
Discussion leader:Hannes Pfeiffer, PhD, Chalmers University

Abstract: Quantum transduction between microwave and optical photons offers the potential to merge the long-range connectivity of optical photons with the deterministic quantum operations of superconducting microwave qubits. A promising approach to achieving this uses an intermediary mechanical mode along with piezo-optomechanical interactions. Traditionally, these transducers are suspended to confine mechanical fields, but this complicates manufacturing and comes with the major challenge of poor thermal anchoring and a trade-off between noise and efficiency. To overcome these issues, we introduce the – to our knowledge – first design of a release-free electro-optomechanical quantum transducer. Our release-free, i.e. non-suspended, design leverages a silicon-on-sapphire (SOS) platform. It combines release-free lithium niobate electromechanical crystals with silicon optomechanical crystals on a sapphire substrate, optimizing thermal anchoring and microwave and mechanical coherence. Despite departing from the traditional suspended transducer paradigm, our release-free design achieves coupling rates sufficient for quantum-level interactions between microwave photons, phonons, and optical photons. Unconventionally, it utilizes high-wavevector mechanical modes tightly confined to the chip surface. Beyond quantum science and engineering, this platform and its design principles could also propel low-power acousto-optic systems in integrated photonics.