Quartz-superconductor quantum electromechanical system

TL;DR

This paper proposes a hybrid quantum system combining a quartz mechanical oscillator with a superconducting qubit, demonstrating ground-state cooling and spectral analysis for quantum control and transduction.

Contribution

It introduces a novel quartz-superconductor electromechanical system and analyzes its potential for ground-state cooling and quantum transduction.

Findings

Feasibility of ground-state cooling via resonant piezoelectric coupling.

Analysis of the qubit's fluorescence spectrum with motional sidebands.

The qubit can serve as both a cooling resource and a transducer.

Abstract

We propose and analyse a quantum electromechanical system composed of a monolithic quartz bulk acoustic wave (BAW) oscillator coupled to a superconducting transmon qubit via an intermediate LC electrical circuit. Monolithic quartz oscillators offer unprecedentedly high effective masses and quality factors for the investigation of mechanical oscillators in the quantum regime. Ground-state cooling of such mechanical modes via resonant piezoelectric coupling to an LC circuit, which is itself sideband cooled via coupling to a transmon qubit, is shown to be feasible. The fluorescence spectrum of the qubit, containing motional sideband contributions due to the couplings to the oscillator modes, is obtained and the imprint of the electromechanical steady-state on the spectrum is determined. This allows the qubit to function both as a cooling resource for, and transducer of, the mechanical oscillator. The results described are relevant to any hybrid quantum system composed of a qubit coupled to two (coupled or uncoupled) thermal oscillator modes.