On quantum-classical equivalence for composed communication problems

  • Authors:
  • Alexander A. Sherstov

  • Affiliations:
  • Department of Computer Sciences, University of Texas at Austin, Austin, Texas

  • Venue:
  • Quantum Information & Computation
  • Year:
  • 2010

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Abstract

An open problem in communication complexity proposed by several authors is to provethat for every Boolean function f, the task of computing f(x ∧ y) has polynomiallyrelated classical and quantum bounded-error complexities. We solve a variant of thisquestion. For every f, we prove that the task of computing, on input x and y, both of thequantities f(x∧y) and f(x∨y) has polynomially related classical and quantum boundederrorcomplexities. We further show that the quantum bounded-error complexity ispolynomially related to the classical deterministic complexity and the block sensitivityof f. This result holds regardless of prior entanglement.