Lower bounds for communication capacities of two-qudit unitary operations

Dominic W. Berry
Phys. Rev. A 76, 062302 – Published 6 December 2007

Abstract

It is known that entangling capacities of bipartite unitary operations may be used to place upper bounds on communication capacities. Here we present alternative definitions of entangling capacities for unitary operations and use them to place lower bounds on the communication capacities of arbitrary bipartite unitaries. Thus entangling capacities may be used to place both upper and lower bounds on the communication capacities for arbitrary bipartite unitaries, allowing them to be more easily estimated. We elucidate the connection between these results and the standard formula for the entanglement assisted capacity of channels. In addition, we present more general methods for producing ensembles for communication from initial states for entanglement creation, and thereby derive sufficient conditions such that the usual forms of entangling capacity provide lower bounds on communication capacities.

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  • Received 9 May 2007

DOI:https://doi.org/10.1103/PhysRevA.76.062302

©2007 American Physical Society

Authors & Affiliations

Dominic W. Berry

  • Centre for Quantum Computer Technology, Macquarie University, Sydney, New South Wales 2109, Australia and Department of Physics, The University of Queensland, St. Lucia, Queensland 4072, Australia

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Vol. 76, Iss. 6 — December 2007

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