Mechanically Detecting and Avoiding the Quantum Fluctuations of a Microwave Field
Quantum fluctuations of the light field used for continuous position detection produces stochastic back-action forces and ultimately limits 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 ± 0.4 dB, and measurement imprecision of a single quadrature of motion 2.4 ± 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.
© 2014 American Association for the Advancement of Science. Received 12 March 2014; accepted 2 May 2014 Published online 15 May 2014. We would like to acknowledge J. Hertzberg, T. Rocheleau, T. Ndukum, and M. Shaw for work on earlier experiments that led to these results. This work is supported by funding provided by the Institute for Quantum Information and Matter, an NSF Physics Frontiers Center with support of the Gordon and Betty Moore Foundation (NSF-IQIM 1125565), by DARPA (DARPA-QUANTUM HR0011-10-1-0066), and by NSF (NSF-DMR 1052647, NSF-EEC 0832819).
Submitted - 1312.4084v1.pdf