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Quantum Backaction Evading Measurement of Collective Mechanical Modes
C F Ockeloen-Korppi1, E Damskägg1, J-M Pirkkalainen1
1Department of Applied Physics, Aalto University, P.O. Box 15100, FI-00076 AALTO, Finland.
Abstract:
The standard quantum limit constrains the precision of an oscillator position measurement. It arises from a balance between the imprecision and the quantum backaction of the measurement. However, a measurement of only a single quadrature of the oscillator can evade the backaction and be made with arbitrary precision. Here we demonstrate quantum backaction 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.
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