Abstract
The optical lever is a centuries old and widely used detection
technique employed in applications ranging from consumer products and
industrial sensors to precision force microscopes used in scientific
research. However, despite the long history, its quantum limits have
yet to be explored. In general, any precision optical measurement is
accompanied by optical force induced disturbance to the measured
object (termed as back action) leading to a standard quantum limit
(SQL). Here, we give a simple ray optics description of how such back
action can be evaded in optical lever detection. We perform a
proof-of-principle experiment demonstrating the mechanism of back
action evasion in the classical regime, by developing a lens system
that cancels extra tilting of the reflected light off a silicon
nitride membrane mechanical resonator caused by
laser-pointing-noise-induced optical torques. We achieve a readout
noise floor two orders of magnitude lower than the SQL, corresponding
to an effective optomechanical cooperativity of 100 without the need
for an optical cavity. As the state-of-the-art ultralow dissipation
optomechanical systems relevant for quantum sensing are rapidly
approaching the level where quantum noise dominates, simple and widely
applicable back action evading protocols will be crucial for pushing
beyond quantum limits.
Funder
National Science Foundation
Charles E. Kaufman
Foundation
Subject
Atomic and Molecular Physics, and Optics,Electronic, Optical and Magnetic Materials
Cited by
1 articles.
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