| Download | - View final version: Beyond the quantum Cramér-Rao bound (PDF, 383 KiB)
- View supplementary information: Beyond the quantum Cramér-Rao bound (PDF, 274 KiB)
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| DOI | Resolve DOI: https://doi.org/10.1103/PhysRevLett.134.010804 |
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| Author | Search for: Hervas, J. R.ORCID identifier: https://orcid.org/0000-0003-4499-7378; Search for: Goldberg, A. Z.1ORCID identifier: https://orcid.org/0000-0002-3301-7672; Search for: Sanz, A. S.ORCID identifier: https://orcid.org/0000-0001-8617-5976; Search for: Hradil, Z.ORCID identifier: https://orcid.org/0000-0001-8732-4638; Search for: Řeháček, J.ORCID identifier: https://orcid.org/0000-0002-4969-2760; Search for: Sánchez-Soto, L. L.ORCID identifier: https://orcid.org/0000-0002-7441-8632 |
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| Affiliation | - National Research Council of Canada. Quantum and Nanotechnologies
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| Funder | Search for: QuantERA; Search for: Kavli Institute for Theoretical Physics, University of California, Santa Barbara; Search for: National Research Council of Canada. Quantum Sensors Challenge program; Search for: Agencia Española de Investigación |
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| Format | Text, Article |
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| Abstract | The quantum Cramér-Rao bound (QCRB) stands as a cornerstone of quantum metrology. Yet, akin to its classical counterpart, it provides only local information and overlooks higher-order details. We leverage the theory of higher-order asymptotics to circumvent these issues, providing corrections to the performance of estimators beyond the QCRB. While the QCRB often yields a whole family of optimal states and several optimal measurements, our approach allows us to identify optimal states and measurements within the family that are otherwise equivalent according to the QCRB alone; these are requisite for optimal metrology before reaching the asymptotic limit. These results are especially pertinent when dealing with unitary processes. |
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| Publication date | 2025-01-10 |
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| Publisher | American Physical Society |
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| Licence | |
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| Language | English |
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| Peer reviewed | Yes |
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| Export citation | Export as RIS |
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| Report a correction | Report a correction (opens in a new tab) |
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| Record identifier | 85e31587-2f2d-4b5f-875c-9e0c769c1723 |
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| Record created | 2025-06-13 |
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| Record modified | 2025-06-13 |
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