Quantum mechanics. Mechanically detecting and avoiding the quantum fluctuations of a microwave field.
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 ± 0.4 decibels (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.
Applied Physics, California Institute of Technology, Pasadena, CA 91125, USA. Kavli Nanoscience Institute, California Institute of Technology, Pasadena, CA 91125, USA.
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J
Suh
Applied Physics, California Institute of Technology, Pasadena, CA 91125, USA. Kavli Nanoscience Institute, California Institute of Technology, Pasadena, CA 91125, USA.
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AJ
Weinstein
Applied Physics, California Institute of Technology, Pasadena, CA 91125, USA. Kavli Nanoscience Institute, California Institute of Technology, Pasadena, CA 91125, USA.
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CU
Lei
Applied Physics, California Institute of Technology, Pasadena, CA 91125, USA. Kavli Nanoscience Institute, California Institute of Technology, Pasadena, CA 91125, USA.
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EE
Wollman
Applied Physics, California Institute of Technology, Pasadena, CA 91125, USA. Department of Physics, University of Arizona, Tucson, AZ 85721, USA.
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SK
Steinke
Department of Physics, University of Arizona, Tucson, AZ 85721, USA.
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P
Meystre
Department of Physics, McGill University, Montreal, Quebec, H3A 2T8 Canada.
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Clerk
Applied Physics, California Institute of Technology, Pasadena, CA 91125, USA. Kavli Nanoscience Institute, California Institute of Technology, Pasadena, CA 91125, USA. schwab@caltech.edu.
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Schwab