Applied Physics

Tinker-Free Interferometry

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Science  14 Dec 2007:
Vol. 318, Issue 5857, pp. 1699
DOI: 10.1126/science.318.5857.1699b

The interference of waves, be they photons, atoms, or electrons, and the measured phase shift induced as the waves take a different route around the arms of an interferometer are widely used in applications ranging from global positioning systems and gravity wave detectors down to the more mundane characterization of optical materials. The sensitivity of the interferometer in measuring the phase shift is affected by noise contributions to the signal. To combat this noise, piezoelectric actuators are typically used to adjust the system to an optimum measuring point for maximum sensitivity. This approach has drawbacks, however, for certain applications where the determination of arbitrary phase shifts is important. Pezzé et al. introduce a method and protocol of photon counting at the output paths to determine the phase. They show that the classical, or thermal, noise can be eliminated without bias (i.e., no tinkering with the phase shift is necessary). At this quantum limit, only quantum uncertainty affects the precision of the phase measurement. — ISO

Phys. Rev. Lett. 99, 223602 (2007).

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