Negative quasiprobabilities enhance phase estimation in quantum-optics experiment

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• Noah Lupu-Gladstein (University of Toronto)
• Friday 05 November 2021, 11:00-12:00
• Virtually, at Zoom.

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Hallmarks of quantum theory, such as operators’ failure to commute, impose fundamental limits on measurement precision. Foundational studies of these limits have pushed measurements and metrology to the bleeding edge. Inspired by a recent foundational result connecting metrology with quasiprobabilities [1], quantum generalizations of probabilities, we discover a filtering technique that promises an—in principle—unlimited advantage in the information rate of trials that survive the filter. We implement this filter in a proof-of-principle optical measurement of a waveplate’s birefringent phase and amplify the information per detected photon by over two orders of magnitude. We find the theoretically unlimited advantage to be bounded in practice because the filter also amplifies systematic errors. We crystallize the relationship between enhanced precision and negative quasiprobabilities by deriving an equality for pure states, confirmed by our data, between the postselected information-rate and a function of a quasiprobability distribution.

[1] D. R. M. Arvidsson-Shukur, N. Yunger Halpern, H. V. Lepage, A. A. Lasek, C. H. W. Barnes, and S. Lloyd, Quantumadvantage in postselected metrology, Nature Communications11, 3775 (2020)

Where: Virtually on Zoom https://us02web.zoom.us/j/88908652048?pwd=MDV3N3k0YnNWMlhKOEk1NDZlUEtaUT09

This talk is part of the Cavendish Quantum Information Seminar Series series.

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