Creation and control of multi-phonon Fock states in a bulk acoustic wave resonator

TL;DR

This paper demonstrates the controlled creation and characterization of multi-phonon Fock states in a macroscopic bulk-acoustic wave resonator, showcasing advanced quantum control of mechanical systems for quantum information applications.

Contribution

It introduces a method for generating and analyzing complex quantum states in a macroscopic acoustic resonator, leveraging long coherence times and selective mode coupling.

Findings

Successful generation of multi-phonon Fock states

Wigner tomography confirms quantum nature of states

Long coherence times enable sophisticated quantum control

Abstract

Quantum states of mechanical motion can be important resources for quantum information, metrology, and studies of fundamental physics. Recent demonstrations of superconducting qubits coupled to acoustic resonators have opened up the possibility of performing quantum operations on macroscopic motional modes, which can act as long-lived quantum memories or transducers. In addition, they can potentially be used to test for novel decoherence mechanisms in macroscopic objects and other modifications to standard quantum theory. Many of these applications call for the ability to create and characterize complex quantum states, putting demanding requirements on the speed of quantum operations and the coherence of the mechanical mode. In this work, we demonstrate the controlled generation of multi-phonon Fock states in a macroscopic bulk-acoustic wave resonator. We also perform Wigner tomography and state reconstruction to highlight the quantum nature of the prepared states. These demonstrations are made possible by the long coherence times of our acoustic resonator and our ability to selectively couple to individual phonon modes. Our work shows that circuit quantum acousto-dynamics (circuit QAD) enables sophisticated quantum control of macroscopic mechanical objects and opens the door to using acoustic modes as novel quantum resources.