Chu leads the Hybrid Quantum Systems Group coupling mechanical resonators to superconducting circuits and diamond color centers. Research directions: (1) Circuit quantum acousto-dynamics (cQAD) — HBAR resonators coupled to transmon qubits achieve single-phonon nonlinearity (coherence/anharmonicity ratio 6.8), mechanical qubit gates demonstrated (arXiv 2406.07360, 2024); (2) Optimal control for high Fock state preparation in bulk resonators; (3) Ultra-cold mechanical quantum sensor — cryogenically cooled nanomechanical oscillators as probes for new physics beyond the standard model; (4) Coupling NV/SiV color centers in diamond to acoustic waves for hybrid quantum memory and transduction. Targets long-lived phonon storage for quantum networking and quantum sensing beyond the standard quantum limit.

Xu leads the Experimental Quantum Engineering group with a joint ETH–PSI appointment. Research directions: (1) Superconducting circuit quantum sensing — using qubits-as-sensors for detecting weak microwave signals beyond standard quantum limits, quantum non-demolition readout of photon fields; (2) Quantum error correction enabled sensing — integrating bosonic codes (cat qubits, binomial codes) into sensing protocols; (3) Quantum acoustics — coupling superconducting qubits to surface acoustic wave (SAW) resonators for hybrid quantum sensing; (4) Novel quantum hardware at PSI — leveraging PSI's infrastructure for cryogenic device fabrication and testing. Connected to the ETH–PSI Quantum Computing Hub.