Quantum advantage in postselected metrology.
Yunger Halpern, Nicole
Lasek, Aleksander A
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Arvidsson Shukur, D., Yunger Halpern, N., Lepage, H., Lasek, A. A., Barnes, C., & Lloyd, S. (2020). Quantum advantage in postselected metrology.. Nature Communications, 11 (1), 3775-3775. https://doi.org/10.1038/s41467-020-17559-w
In every parameter-estimation experiment, the final measurement or the postprocessing incurs a cost. Postselection can improve the rate of Fisher information (the average information learned about an unknown parameter from a trial) to cost. We show that this improvement stems from the negativity of a particular quasiprobability distribution, a quantum extension of a probability distribution. In a classical theory, in which all observables commute, our quasiprobability distribution is real and nonnegative. In a quantum-mechanically noncommuting theory, nonclassicality manifests in negative or nonreal quasiprobabilities. Negative quasiprobabilities enable postselected experiments to outperform optimal postselection-free experiments: postselected quantum experiments can yield anomalously large information-cost rates. This advantage, we prove, is unrealizable in any classically commuting theory. Finally, we construct a preparation-and-postselection procedure that yields an arbitrarily large Fisher information. Our results establish the nonclassicality of a metrological advantage, leveraging our quasiprobability distribution as a mathematical tool.
European Commission Horizon 2020 (H2020) Marie Sk?odowska-Curie actions (642688)
External DOI: https://doi.org/10.1038/s41467-020-17559-w
This record's URL: https://www.repository.cam.ac.uk/handle/1810/308740
Attribution 4.0 International
Licence URL: https://creativecommons.org/licenses/by/4.0/