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SUMMARY:The usefulness of negativity: Quantum advantage in post-selected m
 etrology - David Arvidsson-Shukur\, Cavendish Laboratory\, University of C
 ambridge
DTSTART:20201023T100000Z
DTEND:20201023T110000Z
UID:TALK151264@talks.cam.ac.uk
CONTACT:40340
DESCRIPTION:In this talk\, I will show that post-selection offers a non-cl
 assical advantage in metrology. In every parameter-estimation experiment\,
  the final measurement or the post-processing incurs some cost. Post-selec
 tion can improve the rate of Fisher information (the average information l
 earned about an unknown parameter from an experimental trial) to cost. Thi
 s improvement\, we will see\, stems from the negativity of the Kirkwood-Di
 rac (KD) quasi-probability distribution\, a quantum extension of a probabi
 lity distribution. In a classical theory\, in which all observables commut
 e\, the KD distribution can be expressed as real and non-negative. In a qu
 antum-mechanical theory\, however\, I will show that non-commutation force
 s the KD distribution to include negative or non-real quasi-probabilities.
  The distribution’s non-classically negative values enable post-selected
  experiments to outperform even post-selection-free experiments whose inpu
 t states and final measurements are optimised: Post-selected quantum exper
 iments can yield anomalously large information-cost rates. Finally\, I wil
 l outline a preparation-and-post-selection procedure that can result in an
  arbitrarily large Fisher information. In collaboration with Aephraim Stei
 nberg’s quantum-optics group\, we are currently conducting an experiment
  to demonstrate this result.\n\nReferences\n\n1) D. Arvidsson-Shukur et al
 .\, Nature Comms.\, 11\, 3775\, (2020) https://www.nature.com/articles/s41
 467-020-17559-w \n\n2) https://arxiv.org/abs/1903.02563 \n\n3) https://www
 .cam.ac.uk/research/news/quantum-negativity-can-power-ultra-precise-measur
 ements \n\nZoom Link\n\nPlease click the link below to join the webinar:\n
 https://us02web.zoom.us/j/86846521451?pwd=M0VUSE5wTEJwSndCbEx0VUtqNHpuZz09
 \nPasscode: 226745\n
LOCATION:Virtually\, at Zoom
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