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SUMMARY:Negative quasiprobabilities enhance phase estimation in quantum-op
 tics experiment  - Noah Lupu-Gladstein (University of Toronto)
DTSTART:20211105T110000Z
DTEND:20211105T120000Z
UID:TALK163033@talks.cam.ac.uk
CONTACT:40340
DESCRIPTION:Hallmarks of quantum theory\, such as operators' failure to co
 mmute\, impose fundamental limits on measurement precision. Foundational s
 tudies of these limits have pushed measurements and metrology to the bleed
 ing edge. Inspired by a recent foundational result connecting metrology wi
 th quasiprobabilities [1]\, quantum generalizations of probabilities\, we 
 discover a filtering technique that promises an--in principle--unlimited a
 dvantage in the information rate of trials that survive the filter. We imp
 lement this filter in a proof-of-principle optical measurement of a wavepl
 ate's birefringent phase and amplify the information per detected photon b
 y over two orders of magnitude. We find the theoretically unlimited advant
 age to be bounded in practice because the filter also amplifies systematic
  errors. We crystallize the relationship between enhanced precision and ne
 gative quasiprobabilities by deriving an equality for pure states\, confir
 med by our data\, between the postselected information-rate and a function
  of a quasiprobability distribution.\n\n\n[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 Communications
 11\, 3775 (2020)\n\n\nWhere: Virtually on Zoom https://us02web.zoom.us/j/8
 8908652048?pwd=MDV3N3k0YnNWMlhKOEk1NDZlUEtaUT09
LOCATION:Virtually\, at Zoom
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