Mechanical Resonators Under Stress: Ultralow Dissipation For Quantum Optomechanics

Online Physics Seminar by Dr. Nils Engelsen (École polytechnique fédérale de Lausanne) held on 25 August 2022.
Nanomechanical oscillators are among the most sensitive force and acceleration sensors and show promise as a quantum technology. However, mechanical dissipation fundamentally limits their performance by admitting thermal noise from the environment and decreasing the coherence time of quantum states of the oscillator. Furthermore, reduced resonator mass increases force sensitivity, but the high surface-to-volume ratio of nanoscale devices increases dissipation. In this talk, I will show how engineering the geometry of strained nanomechanical resonators enhances ‘dissipation dilution’ and produces the highest quality factors to date at room temperature: 3.6 billion in Si3N4 nanobeams. Specifically, I will show a range of different design concepts, including phononic crystals and binary trees, which increases quality factors by up to two orders of magnitude. I will then discuss the prospects for quantum-enhanced sensing with mechanical resonators in optomechanical systems.