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Quantum metrology with mixed states: when recovering lost information is better than never losing it

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posted on 2023-06-09, 04:39 authored by Simon A Haine, Stuart S Szigeti
Quantum-enhanced metrology can be achieved by entangling a probe with an auxiliary system, passing the probe through an interferometer, and subsequently making measurements on both the probe and auxiliary system. Conceptually, this corresponds to performing metrology with the purification of a (mixed) probe state. We demonstrate via the quantum Fisher information how to design mixed states whose purifications are an excellent metrological resource. In particular, we give examples of mixed states with purifications that allow (near) Heisenberg-limited metrology and provide examples of entangling Hamiltonians that can generate these states. Finally, we present the optimal measurement and parameter-estimation procedure required to realize these sensitivities (i.e., that saturate the quantum Cramér-Rao bound). Since pure states of comparable metrological usefulness are typically challenging to generate, it may prove easier to use this approach of entanglement and measurement of an auxiliary system. An example where this may be the case is atom interferometry, where entanglement with optical systems is potentially easier to engineer than the atomic interactions required to produce nonclassical atomic states.

History

Publication status

  • Published

File Version

  • Published version

Journal

Physical Review A

ISSN

1050-2947

Publisher

American Physical Society

Issue

3

Volume

92

Page range

2317

Department affiliated with

  • Physics and Astronomy Publications

Research groups affiliated with

  • Atomic, Molecular and Optical Physics Research Group Publications

Full text available

  • Yes

Peer reviewed?

  • Yes

Legacy Posted Date

2017-01-12

First Open Access (FOA) Date

2017-01-12

First Compliant Deposit (FCD) Date

2017-01-12

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