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arXiv · 2605.24108

Bell State Analysis Provides an Optimal Basis Saturating the Quantum Cramer-Rao in Rotation Sensing

Zhuoran Bao·Daniel F. V. James
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Abstract

The second-order anti-coherent state of light is known to saturate the Cramer-Rao Bound (QCRB) for rotation sensing around an arbitrary axis. However, due to the complexity of the state and the inefficiency of state tomography, parameter extraction remains an open problem. In this manuscript, we approach the problem of parameter extraction using pairwise Bell state analysis with an additional path degree of freedom. Due to the transformation property of rotation, only the symmetric Bell states will show up in projection in the final state. We exploit this advantage to develop a scheme for extracting the rotation angle for N=4 and N=6 second-order anti-coherent states.

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Zhuoran Bao, Daniel F. V. James. 2026-05-22. Bell State Analysis Provides an Optimal Basis Saturating the Quantum Cramer-Rao in Rotation Sensing. https://arxiv.org/abs/2605.24108

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