Non-Hermitian-enhanced quantum sensing in an optical interferometer

• URL: http://arxiv.org/abs/2607.23978v1
• Date: Mon, 27 Jul 2026 04:03:13 GMT
• Title: Non-Hermitian-enhanced quantum sensing in an optical interferometer
• Abstract summary: We experimentally realize quantum parameter estimation using a non-Hermitian observable on a linear optical platform.<n>We observe a reduced error-propagation variance compared with the optimal Hermitian observable for the same probe-state model.
• Score: 11.71545307490769
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: The precision of quantum parameter estimation is traditionally constrained by the quantum Cramér-Rao bound, which is based on the Hermitian measurement framework. Recent studies of non-Hermitian systems have suggested new possibilities for enhancing parameter-estimation sensitivity. Here, we experimentally realize quantum parameter estimation using a non-Hermitian observable on a linear optical platform. The parameter is encoded in single-photon probe states and read out with a Sagnac interferometer, which allows us to reconstruct the complex expectation value of the implemented non-Hermitian observable from interference fringes. We observe a reduced error-propagation variance compared with the optimal Hermitian observable for the same probe-state model. This advantage remains visible under amplitude-damping noise. We further analyze the complete optical measurement as a physical positive-operator-valued measure (POVM) and show, through the corresponding classical Fisher information (CFI), that the observed non-Hermitian advantage is consistent with the standard quantum metrological limit when all output ports are included. Our results provide an experimental route to non-Hermitian observable readout and clarify its operational meaning in quantum sensing.

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