title: Quantum-limited mirror-motion estimation.
abstract: We experimentally demonstrate optomechanical motion and force measurements near the quantum precision limits set by the quantum Cramér-Rao bounds. Optical beams in coherent and phase-squeezed states are used to measure the motion of a mirror under an external stochastic force. Utilizing optical phase tracking and quantum smoothing techniques, we achieve position, momentum, and force estimation accuracies close to the quantum Cramér-Rao bounds with the coherent state, while the estimation using squeezed states shows clear quantum enhancements beyond the coherent-state bounds.
authors.affiliation: Department of Applied Physics, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Kohjiro
authors.initials: K
authors.lastname: Iwasawa
authors.forename: Kenzo
authors.initials: K
authors.lastname: Makino
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Yonezawa
authors.forename: Mankei
authors.initials: M
authors.lastname: Tsang
authors.forename: Aleksandar
authors.initials: A
authors.lastname: Davidovic
authors.forename: Elanor
authors.initials: E
authors.lastname: Huntington
authors.forename: Akira
authors.initials: A
authors.lastname: Furusawa