  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.
