The precision of quantum parameter estimation is traditionally constrained by the quantum Cram\'{e}r-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.
(English) Quantum mechanics both constrains and empowers precision measurement: the uncertainty principle imposes fundamental limits on parameter estimation, which quantum resources such as entanglement and superposition can saturate. Quantum metrology develops protocols that exploit non-classical probe states and opti...
Non-Hermitian dynamics can sharply amplify the response of a quantum sensor near eigenstate coalescence, but whether this amplification yields a genuine metrological gain depends on how the non-unitary evolution is physically realised and how its resources are counted. We address this question experimentally by imp...
Y. Zhai, Chao Wei, Jun-Da Song et al.· Chinese Physics B· 0 citations
The goal of quantum metrology is to estimate an unknown parameter with better-than-classical precision and, ideally, to attain Heisenberg scaling. In realistic settings, however, noise can substantially reduce this advantage and, in many cases, restore standard-quantum-limit-like performance. Preserving the quantum enh...
Ugne Liaubaite, Debora Ramacciotti, R. Raussendorf· 0 citations
We investigate phase estimation in an SU(1,1) interferometer employing $m$-photon-added even and odd coherent states as nonclassical input resources. The phase sensitivity is evaluated through intensity detection and the error propagation method, while the ultimate precision limit is determined from the quantum Cram\'e...
Abdelmajid El Maaroufi, M. A. Maskour, B. Maroufi et al.· 0 citations
Quantum interferometry provides a pivotal method for investigating complex photon-photon interaction, enabling various quantum information technologies that beyond the possibilities of classical physics. While such an effective interaction is mostly studied in N × N unitary transformation, m × n nonunitary transformati...
Quantum-enhanced sensing with atomic ensembles has predominantly focused on qubit-based protocols, despite the growing ability of many experimental platforms to coherently control and entangle multi-level systems. Here, we investigate quantum-enhanced sensing with qutrit ensembles by introducing three experimentally fe...
Deepshikha Datta, Sayam Chakraborty, J. D. Wilson et al.· 0 citations
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