On approximation of infinite-dimensional quantum channels

  • Authors:
  • M. E. Shirokov;A. S. Holevo

  • Affiliations:
  • Steklov Mathematical Institute, RAS, Moscow, Russia;Steklov Mathematical Institute, RAS, Moscow, Russia

  • Venue:
  • Problems of Information Transmission
  • Year:
  • 2008

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Abstract

We develop an approximation approach to infinite-dimensional quantum channels based on a detailed investigation of continuity properties of entropic characteristics of quantum channels and operations (trace-nonincreasing completely positive maps) as functions of a pair "channel, input state." Obtained results are then applied to the problems of continuity of the 驴-capacity as a function of a channel, strong additivity of the 驴-capacity for infinite-dimensional channels, and approximating representation for the convex closure of the output entropy of an arbitrary quantum channel.