We demonstrate a transducer of nanomechanical motion based on cavity enhanced optical near-fields capable of achieving a shot-noise limited imprecision more than 10 dB below the standard quantum limit (SQL). Residual background due to fundamental thermodynamical frequency fluctuations allows a total imprecision 3 dB below the SQL at room temperature (corresponding to 600 am/Hz^(1/2) in absolute units) and is known to reduce to negligible values for moderate cryogenic temperatures. The transducer operates deeply in the quantum backaction dominated regime, prerequisite for exploring quantum backaction, measurement-induced squeezing and accessing sub-SQL sensitivity using backaction evading techniques.
@article{arxiv.1003.3752,
title = {Measuring nanomechanical motion with an imprecision far below the standard quantum limit},
author = {G. Anetsberger and E. Gavartin and O. Arcizet and Q. P. Unterreithmeier and E. M. Weig and M. L. Gorodetsky and J. P. Kotthaus and T. J. Kippenberg},
journal= {arXiv preprint arXiv:1003.3752},
year = {2015}
}