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SUMMARY:Finite blocklength converse bounds for quantum channels - Will Mat
 thews (University of Cambridge)
DTSTART:20121011T131500Z
DTEND:20121011T141500Z
UID:TALK40584@talks.cam.ac.uk
CONTACT:Paul Skrzypczyk
DESCRIPTION:I'll talk about joint work with Stephanie Wehner in which we d
 erive upper bounds on the rate of transmission of classical information ov
 er quantum channels by block codes with a given blocklength and error prob
 ability\, for both entanglement-assisted and unassisted codes\, in terms o
 f a unifying framework of quantum hypothesis testing with restricted measu
 rements. Our bounds do not depend on any special property of the channel (
 such as memorylessness) and generalise both a classical converse of Polyan
 skiy\, Poor\, and Verdu as well as a quantum converse of Renner and Wang\,
  and have a number of desirable properties. In particular our bound on ent
 anglement-assisted codes is a semidefinite program and for memoryless chan
 nels its large n limit is the well known formula for entanglement-assisted
  capacity due to Bennett\, Shor\, Smolin and Thapliyal.
LOCATION:MR4\, Centre for Mathematical Sciences
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