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SUMMARY:Tradeoff relations between accessible information\, informational 
 power\, and purity - Michele Dall'Arno
DTSTART:20200116T141500Z
DTEND:20200116T151500Z
UID:TALK137671@talks.cam.ac.uk
CONTACT:Johannes Bausch
DESCRIPTION:The accessible information and the informational power quantif
 y the maximum amount of information that can be extracted from a quantum e
 nsemble and by a quantum measurement\, respectively. Here\, we investigate
  the tradeoff between the accessible information (informational power\, re
 spectively) and the purity of the states of the ensemble (the elements of 
 the measurement\, respectively). Under any given lower bound on the purity
 \, i) we compute the minimum informational power and show that it is attai
 ned by the depolarized uniformly-distributed measurement\; ii) we give a l
 ower bound on the accessible information. Under any given upper bound on t
 he purity\, i) we compute the maximum accessible information and show that
  it is attained by an ensemble of pairwise commuting states with at most t
 wo distinct non-null eigenvalues\; ii) we give a lower bound on the maximu
 m informational power. The present results provide\, as a corollary\, nove
 l sufficient conditions for the tightness of the Jozsa-Robb-Wootters lower
  bound to the accessible information.
LOCATION:MR15\, Centre for Mathematical Sciences\, Wilberforce Road\, Camb
 ridge
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