Nanoscale Torsional Dissipation Dilution for Quantum Experiments and Precision Measurement

Abstract

The quest for ultrahigh-Q nanomechanical resonators has driven intense study of strain-induced dissipation dilution, an effect whereby vibrations of a tensioned plate are effectively trapped in a lossless potential. Here, we show for the first time that torsion modes of nanostructures can experience dissipation dilution, yielding a new class of ultrahigh-Q nanomechanical resonators with broad applications to quantum experiments and precision measurement. Specifically, we show that torsion modes of strained nanoribbons have Q factors scaling as their width-to-thickness ratio squared (characteristic of "soft clamping"), yielding Q factors as high as 108 and Q-frequency products as high as 1013 Hz for devices made of Si3N4. Using an optical lever, we show that the rotation of one such nanoribbon can be resolved with an imprecision 100 times smaller than the zero-point motion of its fundamental torsion mode, without the use of a cavity or interferometric stability. We also show that a strained nanoribbon can be mass loaded without changing its torsional Q. We use this strategy to engineer a chip-scale torsion pendulum with an ultralow damping rate of 7 μHz and show how it can be used to sense micro-g fluctuations of the local gravitational field. Our findings signal the potential for a new field of imaging-based quantum optomechanics, demonstrate that the utility of strained nanomechanics extends beyond force microscopy to inertial sensing, and hint that the landscape for dissipation dilution remains largely unexplored.