Mechanically detecting and avoiding the quantum fluctuations of a microwave field

J. Suh, A. J. Weinstein, C. U. Lei, E. E. Wollman, S. K. Steinke, P. Meystre, A. A. Clerk, K. C. Schwab

Research output: Contribution to journalArticlepeer-review

106 Scopus citations


Quantum fluctuations of the light field used for continuous position detection produce stochastic back-action forces and ultimately limit the sensitivity. To overcome this limit, the back-action forces can be avoided by giving up complete knowledge of the motion, and these types of measurements are called "back-action evading" or "quantum nondemolition" detection. We present continuous two-tone back-action evading measurements with a superconducting electromechanical device, realizing three long-standing goals: detection of back-action forces due to the quantum noise of a microwave field, reduction of this quantum back-action noise by 8.5 T 0.4 decibels (dB), and measurement imprecision of a single quadrature of motion 2.4 T 0.7 dB below the mechanical zero-point fluctuations. Measurements of this type will find utility in ultrasensitive measurements of weak forces and nonclassical states of motion.

Original languageEnglish (US)
Pages (from-to)1262-1265
Number of pages4
Issue number6189
StatePublished - 2014
Externally publishedYes

ASJC Scopus subject areas

  • General


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