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arXiv · 0804.0087

Beating the standard quantum limit: Phase super-sensitivity of N-photon interferometers

Ryo Okamoto·Holger F. Hofmann·Tomohisa Nagata·Jeremy L. O'Brien·Keiji Sasaki·Shigeki Takeuchi
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Abstract

Quantum metrology promises greater sensitivity for optical phase measurements than could ever be achieved classically. Here we present a theory of the phase sensitivity for the general case where the detection probability is given by an $N$ photon interference fringe. We find that the phase sensitivity has a complex dependence on both the intrinsic efficiency of detection $η$ and the interference fringe visibility $V$. Most importantly, the phase that gives maximum phase sensitivity is in general not the same as the phase at which the slope of the interference fringe is a maximum, as has previously been assumed. We determine the parameter range where quantum enhanced sensitivity can be achieved. In order to illustrate these theoretical results, we perform a four photon experiment with $η=3/4$ and $V=82\pm6$% (an extension of our previous work [Science \textbf{316}, 726 (2007)]) and find a phase sensitivity 1.3 times greater than the standard quantum limit at a phase different to that which gives maximum slope of the interference fringe.

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Ryo Okamoto, Holger F. Hofmann, Tomohisa Nagata, Jeremy L. O'Brien, Keiji Sasaki, Shigeki Takeuchi. 2008-04-01. Beating the standard quantum limit: Phase super-sensitivity of N-photon interferometers. https://doi.org/10.1088/1367-2630%2F10%2F7%2F073033

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