title: Quantum Nondemolition Measurement of a Quantum Squeezed State Beyond the 3 dB Limit.
abstract: We use a reservoir engineering technique based on two-tone driving to generate and stabilize a quantum squeezed state of a micron-scale mechanical oscillator in a microwave optomechanical system. Using an independent backaction-evading measurement to directly quantify the squeezing, we observe 4.7±0.9  dB of squeezing below the zero-point level surpassing the 3 dB limit of standard parametric squeezing techniques. Our measurements also reveal evidence for an additional mechanical parametric effect. The interplay between this effect and the optomechanical interaction enhances the amount of squeezing obtained in the experiment.
authors.affiliation: Applied Physics, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: C U
authors.initials: CU
authors.lastname: Lei
authors.affiliation: Applied Physics, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: A J
authors.initials: AJ
authors.lastname: Weinstein
authors.affiliation: Korea Research Institute of Standards and Science, Daejeon 305-340, Republic of Korea.
authors.forename: J
authors.initials: J
authors.lastname: Suh
authors.affiliation: Applied Physics, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: E E
authors.initials: EE
authors.lastname: Wollman
authors.affiliation: Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstrasse 7, D-91058 Erlangen, Germany.|Max Planck Institute for the Science of Light Günther-Scharowsky-Straße 1/Bau 24, D-91058 Erlangen, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Kronwald
authors.affiliation: Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstrasse 7, D-91058 Erlangen, Germany.|Max Planck Institute for the Science of Light Günther-Scharowsky-Straße 1/Bau 24, D-91058 Erlangen, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Marquardt
authors.affiliation: Department of Physics, McGill University, Montreal, Quebec, H3A 2T8 Canada.
authors.forename: A A
authors.initials: AA
authors.lastname: Clerk
authors.affiliation: Applied Physics, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: K C
authors.initials: KC
authors.lastname: Schwab