Quantum back-action evading measurement of collective mechanical modes

  1. C. F. Ockeloen-Korppi,
  2. E. Damskägg,
  3. J.-M. Pirkkalainen,
  4. A. A. Clerk,
  5. M. J. Woolley,
  6. and M. A. Sillanpää
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.
arxiv pdf

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