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arXiv · 0710.2922

Experimental demonstration of phase measurement precision beating standard quantum limit by projection measurement

F. W. Sun·B. H. Liu·Y. X. Gong·Y. F. Huang·Z. Y. Ou·G. C. Guo
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Abstract

We propose and demonstrate experimentally a projection scheme to measure the quantum phase with a precision beating the standard quantum limit. The initial input state is a twin Fock state $|N,N>$ proposed by Holland and Burnett [Phys. Rev. Lett. {\bf 71}, 1355 (1993)] but the phase information is extracted by a quantum state projection measurement. The phase precision is about $1.4/N$ for large photon number $N$, which approaches the Heisenberg limit of 1/N. Experimentally, we employ a four-photon state from type-II parametric down-conversion and achieve a phase uncertainty of $0.291\pm 0.001$ beating the standard quantum limit of $1/\sqrt{N} = 1/2$ for four photons.

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F. W. Sun, B. H. Liu, Y. X. Gong, Y. F. Huang, Z. Y. Ou, G. C. Guo. 2007-10-15. Experimental demonstration of phase measurement precision beating standard quantum limit by projection measurement. https://doi.org/10.1209/0295-5075%2F82%2F24001

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