Optically measuring force near the standard quantum limit

The Heisenberg uncertainty principle sets a lower bound on the noise in a force measurement based on continuously detecting a mechanical oscillator's position. This bound, the standard quantum limit, can be reached when the oscillator subjected to the force is unperturbed by its environment and...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 2014-06, Vol.344 (6191), p.1486-1489
Main Authors: Schreppler, Sydney, Spethmann, Nicolas, Brahms, Nathan, Botter, Thierry, Barrios, Maryrose, Stamper-Kurn, Dan M.
Format: Article
Language:English
Subjects:
Calibration
Charge carriers
Electrons
Gravity
Hall effect
Measurement techniques
Mechanical oscillators
Nanotechnology
Noise measurement
Noise spectra
Optical properties
Phonons
Physicists
Quantum physics
Shot noise
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Summary:The Heisenberg uncertainty principle sets a lower bound on the noise in a force measurement based on continuously detecting a mechanical oscillator's position. This bound, the standard quantum limit, can be reached when the oscillator subjected to the force is unperturbed by its environment and when measurement imprecision from photon shot noise is balanced against disturbance from measurement back-action. We applied an external force to the center-of-mass motion of an ultracold atom cloud in a high-finesse optical cavity and measured the resulting motion optically. When the driving force is resonant with the cloud's oscillation frequency, we achieve a sensitivity that is a factor of 4 above the standard quantum limit and consistent with theoretical predictions given the atoms' residual thermal disturbance and the photodetection quantum efficiency.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.1249850