Description
In many quantum information settings, quantum systems consist of three key components—states, process, and detectors—the precise estimation of which is essential for benchmarking device performance, mitigating errors, and enabling improvements toward utility-scale quantum technologies. The precise estimation of quantum states has been addressed by the state quantum Fisher Information (sQFI) formalism, known to set a theoretical limit to estimation precision and identify the most precise measurements. It has seen wide-ranging applications across quantum sensing and metrology, with the seminal paper cited more than 6,000 times—underscoring its foundational importance. In stark contrast, the analogous information-theoretic precision bounds for detector estimation have remain unknown. While prior studies have demonstrated detector tomography in the framework of classical estimation theory, their precision falls well short of the ideal and no clear guideline exists regarding its quantum-enabled enhancement.
In this work, we solve this problem by introducing a theoretical framework for efficient detector estimation, centred around a newly introduced quantity: the detector quantum Fisher information (dQFI). This work reveals the fundamental limit of precision achievable in estimating quantum measurements and identifies the optimal probe states. The dQFI highlights aspects of detector analysis that fundamentally differ from quantum state estimation. Through proofs, examples, and experimental validation, we demonstrate the relevance and robustness of our proposal for current quantum detector technologies. By formalising a dual perspective to state estimation, our framework completes and connects the triad of efficient state, process, and detector tomography, advancing quantum information theory with broader implications for emerging technologies reliant on precisely calibrated measurements.
| I am the presenting author | Yes |
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