Measuring nanomechanical motion with a microwave cavity interferometer

Understand

In recent years microfabricated microwave cavities have been extremely successful in a wide variety of detector applications.

• In this article we focus this technology on the challenge of quantum-limited displacement detection of a macroscopic object.
• We measure the displacement of a nanomechanical beam by capacitively coupling its position to the resonant frequency of a superconducting transmission-line microwave cavity.
• With our device we realize near state-of-the-art mechanical force sensitivity (3 $\rm{aN/\sqrt{Hz}}$) and thus add to only a handful of techniques able to measure thermomechanical motion at 10's of milliKelvin temperatures.