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Journal of Optics B Quantum and Semiclassical Optics

Reaching quantum limits for phase-shift detection with semiclassical states

Alfredo Luis

Published Sep 23, 2003• 8 citations
Publisher

Abstract

We present two measuring strategies reaching the Heisenberg limit for phase-shift measurements using semiclassical coherent states exclusively. We examine their performance by assuming practical experimental conditions such as losses and nonideal detectors.
DOI
10.1088/1464-4266/6/1/001

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We analyze the quantum limit to the sensitivity of the detection of small displacements. We focus on the case of free particles and harmonic oscillators as the systems experiencing the displacement. We show that the minimum displacement detectable is proportional to the inverse of the square root of the mean value of the energy in the state experiencing the displacement (Heisenberg limit). We present a measuring scheme that reaches this limit using semiclassical states. We examine the performance of this strategy under realistic practical conditions by computing the effect of imperfections such as losses and nonunit detection efficiencies. This analysis confirms the robustness of this measuring strategy by showing that the experimental imperfections can be suitably compensated by increasing the mean energy of the input state.