Superior Frequency Stability and Long-Lived State-Swapping in Cubic-SiC Mechanical Mode Pairs

TL;DR

This paper demonstrates nearly degenerate mechanical mode pairs in a cubic-SiC system with high stability, long lifetimes, and efficient state-swapping, advancing quantum phononic device development.

Contribution

It introduces a cavity electromechanical system with nearly degenerate modes in cubic-SiC, achieving high quality factors and long-lived states for quantum applications.

Findings

Mechanical modes with quality factors up to 10^8.

Frequency stability surpassing other optomechanical devices.

State-swapping efficiency over 78%.

Abstract

The multimode cavity optomechanical system offers versatile applications including state transduction, coherent interconnection, and many-body simulations. In this study, we developed a cavity electromechanical system that integrates a 3C-SiC membrane and a rectangular superconducting cavity to observe the generation of nearly degenerate pairs of mechanical modes. Subsequently, we derive the expression for intrinsic frequency under nonuniform stress and find that this method supports a remarkably resolution for stress analysis in thin films. Experimentally, we perform collective fitting on the measured set of 57 mechanical modes, revealing deviations in biaxial non-uniform stress on the order of MPa. These degeneracy-broken mechanical modes exhibit exceptional quality factors as high as $10^8$ in a thermal bath of 10 mK. Furthermore, Allan deviation indicates that these modes exhibit extremely stable frequencies compared with different types of optomechanical devices. We then performed state-swapping between near-degenerate mode pairs, demonstrating the transfer efficiency exceeding 78\%, attributed to their exceptionally long lifetimes. This study paves the way for the design of compact quantum phononic devices featuring high-quality-factor mechanical multimode.