Measuring nanomechanical motion with an imprecision far below the standard quantum limit

TL;DR

This paper reports a nanomechanical motion transducer that surpasses the standard quantum limit in measurement precision using cavity-enhanced optical near-fields, enabling quantum backaction studies and sub-SQL sensitivity.

Contribution

The work introduces a transducer capable of achieving shot-noise limited imprecision well below the SQL, with potential for quantum measurement applications at room and cryogenic temperatures.

Findings

Imprecision more than 10 dB below SQL

Total imprecision 3 dB below SQL at room temperature

Operates in the quantum backaction dominated regime

Abstract

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.