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DTSTART:20230312T070000
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DTSTART;TZID=America/Toronto:20231016T150000
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URL:https://uwaterloo.ca/institute-for-quantum-computing/events/fully-quant
 um-learning-comparison-unknown-unitary-channels
LOCATION:QNC - Quantum Nano Centre 200 University Avenue West 0101 Waterloo
  ON N2L 3G1 Canada
SUMMARY:Fully-quantum learning: Comparison of unknown unitary channels with
 \nmultiple uses
CLASS:PUBLIC
DESCRIPTION:IQC COLLOQUIUM - MIO MURAO\, THE UNIVERSITY OF TOKYO\n\nQuantum
  Nano Centre (QNC) Room 0101 200 University Ave West\, Waterloo\nOntario\n
 \nPlease note start time 3:00 PM\n\nEfficiently learning properties of unk
 nown quantum objects is a\nfundamental task in quantum mechanics and quant
 um information. When\nthere are two unknown quantum objects\, and if we wa
 nt to learn just\nthe relationship between the objects\, a method to direc
 tly compare the\ntwo objects without identifying their descriptions is pre
 ferable\,\nespecially when the number of available copies of each target o
 bject\nis limited. In this work\, we investigate the comparison of unknown
 \nunitary channels with multiple uses of the unitary channels based on\nth
 e quantum tester formalism.  We obtain the optimal minimum-error\nstrateg
 y and the optimal unambiguous strategy of unitary comparison of\ntwo unkno
 wn d-dimensional unitary channels when the number of uses of\nthe channels
  satisfies a certain condition. These optimal strategies\nare implemented 
 by parallel uses of the unitary channels\, even though\nall sequential and
  adaptive strategies implementable by the quantum\ncircuit model are consi
 dered. When the number of the smaller uses of\nthe unitary channels is fix
 ed\, the optimal averaged success\nprobability is achieved by a certain nu
 mber of uses of the other\nchannel. This feature contrasts with the case o
 f pure-state\ncomparison\, where adding more copies of the unknown pure st
 ates always\nimproves the optimal averaged success probability. It highlig
 hts the\ndifference between corresponding tasks for states and channels\, 
 which\nhas been previously shown for quantum discrimination tasks.  \n\nR
 eference: Y. Hashimoto\, A. Soeda and M. Murao\, Comparison of unknown\nun
 itary channels with multiple uses\, arXiv:2208.12519
DTSTAMP:20260406T145150Z
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