All-mechanical quantum noise cancellation for accelerometry: broadband   with momentum measurements, narrow band without
  We show that the ability to make direct measurements of momentum, in addition to the usual direct measurements of position, allows a simple configuration of two identical mechanical oscillators to be used for broadband back-action-free force metrology. This would eliminate the need for an optical reference oscillator in the scheme of Tsang and Caves [Phys. Rev. Lett. 105, 123601 (2010)], along with its associated disadvantages. We also show that if one is restricted to position measurements alone then two copies of the same two-oscillator configuration can be used for narrow-band back-action-free force metrology. 
Kurt Jacobs, Nikolas Tezak, Hideo Mabuchi, Radhakrishnan Balu
quant-ph