Measuring nanomechanical motion with a microwave cavity interferometer

• Published in: Nature physics Vol. 4; no. 7; pp. 555 - 560
• Main Authors: Lehnert, K. W, Regal, C. A, Teufel, J. D
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.07.2008; Nature Publishing Group
• Subjects: Atomic; Classical and Continuum Physics; Complex Systems; Condensed Matter Physics; Fluctuations; Freezing; Mathematical and Computational Physics; Measurement techniques; Molecular; Nanotechnology; Optical and Plasma Physics; Oscillators; Physics; Physics and Astronomy; Quantum theory; Theoretical; Transmission lines
• DOI: 10.1038/nphys974
• ISSN: 1745-2473

A mechanical resonator is a physicist’s most tangible example of a harmonic oscillator. With the advent of micro and nanoscale mechanical resonators, researchers are rapidly progressing towards a tangible harmonic oscillator with motion that requires a quantum description. Challenges include freezing out the thermomechanical motion to leave only zero-point quantum fluctuations δ x zp and, equally importantly, realizing a Heisenberg-limited displacement detector. Here, we introduce a detector that can be in principle quantum limited and is also capable of efficiently coupling to the motion of small-mass, nanoscale objects, which have the most accessible zero-point motion. Specifically, we measure the displacement of a nanomechanical beam using a superconducting transmission-line microwave cavity. We realize excellent mechanical force sensitivity (3 aN Hz −1/2 ), detect thermal motion at tens of millikelvin temperatures and achieve a displacement imprecision of 30 times the standard quantum limit. Measurements of the position of a nanoscale beam using a microwave cavity detector represents a promising step towards being able to measure displacements at the quantum limit.