Phononic bath engineering of a superconducting qubit

Interactions between a quantum system and its lossy environment typically lead to unwanted decoherence and dissipation. However, in certain contexts, controlled dissipation can be harnessed for the preparation and manipulation of quantum systems. This type of quantum bath engineering has been advantageously leveraged in a broad class of systems including neutral atoms and trapped ions, optomechanical devices and superconducting qubits. Quantum acoustic systems, in which superconducting qubits are coupled to quantized mechanical degrees of freedom, offer a unique paradigm for engineering dissipation to control quantum information using tailor-made phononic loss channels. Here we demonstrate quantum state preparation and stabilization of a superconducting transmon qubit through its dissipative interaction with an engineered phononic bath of piezoelectric surface acoustic waves. We achieve this using a hybrid quantum system composed of a superconducting qubit coupled to a piezoelectric surface acoustic wave resonator to enable dynamical stabilization of an arbitrary superposition state of the qubit via its interaction with itinerant piezo-phonons.