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Intrinsic noise properties of atomic point contact displacement detectors

N. E. Flowers-Jacobs·D. R. Schmidt·K. W. Lehnert
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Abstract

We measure the noise added by an atomic point contact operated as a displacement detector. With a microwave technique, we increase the measurement speed of atomic point contacts by a factor of 500. The measurement is then fast enough to detect the resonant motion of a nanomechanical beam at frequencies up to 60 MHz and sensitive enough to observe the random thermal motion of the beam at 250 mK. We demonstrate a shot-noise limited imprecision of $2.3\pm0.1\ \mathrm{fm/\sqrt{Hz}}$ and observe a $78\pm20 \mathrm{aN/\sqrt{Hz}}$ backaction force, yielding a total uncertainty in the beam's displacement that is $42\pm9$ times the standard quantum limit.

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N. E. Flowers-Jacobs, D. R. Schmidt, K. W. Lehnert. 2007-01-23. Intrinsic noise properties of atomic point contact displacement detectors. https://doi.org/10.1103/physrevlett.98.096804

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