Quantum Fisher information and resource accounting
Research context
postgraduate concept · conditional · As of 2026-10-10
For ν independent repetitions of a specified parameter-encoding state/channel, a locally unbiased estimator obeys Var(θ̂)≥1/(νF_Q) when the regularity assumptions apply.
Key knowledge
For ν independent repetitions of a specified parameter-encoding state/channel, a locally unbiased estimator obeys Var(θ̂)≥1/(νF_Q) when the regularity assumptions apply. Entanglement can improve ideal unitary phase sensitivity, but preparation, total interrogation time, loss and control count as resources. An ideal Heisenberg scaling is not a universal instrument uncertainty claim.
Values and equations
Var(θ̂)≥1/(νF_Q)
- θ̂
- Parameter estimator; parameter units
- F_Q
- Quantum Fisher information; inverse squared parameter units
- ν
- Independent repetitions
Conditions and scope
- Single identifiable parameter and local/asymptotic attainability; F_Q has reciprocal squared parameter units.
- Multiparameter incompatibility, finite-sample bias and noise change attainable bounds. Compare equal total physical resources and include calibration/traceability uncertainty separately.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
- Quantum metrology (2006; 2005 preprint)Vittorio Giovannetti, Seth Lloyd and Lorenzo MacconeResearch paper
- General framework for estimating the ultimate precision limit in noisy quantum-enhanced metrologyB. M. Escher, R. L. de Matos Filho and L. Davidovich / Universidade Federal do Rio de JaneiroResearch paper
Evidence and review
Inspected parameter encoding, Cramér–Rao resource limits and independent/entangled strategies; source check dated 2026-10-10. Scope is limited to the cited statements, equations and assumptions, not the whole publication. Inspected channel/Kraus precision bound and photon-loss example; noise-dependent scope; source check dated 2026-10-10. Scope is limited to the cited statements, equations and assumptions, not the whole publication.
2026-10-10 · Author source inspection of the displayed claim, model assumptions and equations; independent exact-content and branch-inventory review is a separate gate. Contemporary status is a dated snapshot, not a promise of ongoing monitoring.
Entry details
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- research-measurement-quantum-fisher-resources
- Revision
- research.1
- Structured reference record
- Postgraduate & research reference