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arXiv · 1405.2397

Enhanced interferometry using squeezed thermal states and even or odd states

Qing-Shou Tan·Jie-Qiao Liao·Xiaoguang Wang·Franco Nori
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Abstract

We derive a general expression of the quantum Fisher information for a Mach-Zehnder interferometer, with the port inputs of an \emph{arbitrary} pure state and a squeezed thermal state. We find that the standard quantum limit can be beaten, when even or odd states are applied to the pure-state port. In particular, when the squeezed thermal state becomes a thermal state, all the even or odd states have the same quantum Fisher information for given photon numbers. For a squeezed thermal state, optimal even or odd states are needed to approach the Heisenberg limit. As examples, we consider several common even or odd states: Fock states, even or odd coherent states, squeezed vacuum states, and single-photon-subtracted squeezed vacuum states. We also demonstrate that super-precision can be realized by implementing the parity measurement for these states.

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Qing-Shou Tan, Jie-Qiao Liao, Xiaoguang Wang, Franco Nori. 2014-05-10. Enhanced interferometry using squeezed thermal states and even or odd states. https://doi.org/10.1103/physreva.89.053822

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