2016/08/31 by C. F. Ockeloen-Korppi, E. Damskägg, J. -M. Pirkkalainen +3
Physics and Astronomy · #cond-mat.mes-hall #quant-ph
paper · pdf · doi:10.1103/physrevlett.117.140401
published as Phys. Rev. Lett. 117, 140401 (2016) · 6 pages, 4 figures and supplement
arxiv created 2016/09/27 · arxiv updated 2016/09/28
The standard quantum limit constrains the precision of an oscillator position measurement. It arises from a balance between the imprecision and the quantum back-action of the measurement. However, a measurement of only a single quadrature of the oscillator can evade the back-action and be made with arbitrary precision. Here we demonstrate quantum back-action evading measurements of a collective quadrature of two mechanical oscillators, both coupled to a common microwave cavity. The work allows for quantum state tomography of two mechanical oscillators, and provides a foundation for macroscopic mechanical entanglement and force sensing beyond conventional quantum limits.