The operational meaning of min- and max-entropy

  • Authors:
  • Robert König;Renato Renner;Christian Schaffner

  • Affiliations:
  • Institute for Quantum Information, California Institute of Technology, Pasadena, CA;Institute for Theoretical Physics, ETH Zurich, Zurich, Switzerland;Centrum Wiskunde & Informatica, Amsterdam, The Netherlands

  • Venue:
  • IEEE Transactions on Information Theory
  • Year:
  • 2009

Quantified Score

Hi-index 755.02

Visualization

Abstract

In this paper, we show that the conditional min-entropy Hmin (A\B)of a bipartite state ρAB is directly related to the maximum achievable overlap with a maximally entangled state if only local actions on the B-part of ρAB are allowed. In the special case where A is classical, this overlap corresponds to the probability of guessing A given B. In a similar vein, we connect the conditional max-entropy Hmax (A\B) to the maximum fidelity of ρAB with a product state that is completely mixed on A. In the case where A is classical, this corresponds to the security of A when used as a secret key in the presence of an adversary holding B.Because min- and max-entropies are known to characterize information-processing tasks such as randomness extraction and state merging, our results establish a direct connection between these tasks and basic operational problems. For example, they imply that the (logarithm of the) probability of guessing A given B is a lower bound on the number of uniform secret bits that can be extracted from A relative to an adversary holding B.