On Quantum Versions of the Yao Principle

  • Authors:
  • Mart de Graaf;Ronald de Wolf

  • Affiliations:
  • -;-

  • Venue:
  • STACS '02 Proceedings of the 19th Annual Symposium on Theoretical Aspects of Computer Science
  • Year:
  • 2002

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Abstract

The classical Yao principle states that the complexity R驴(f) of an optimal randomized algorithm for a function f with success probability 1 - 驴 equals the complexity max碌 D驴碌 (f) of an optimal deterministic algorithm for f that is correct on a fraction 1 - 驴 of the inputs, weighed according to the hardest distribution 碌 over the inputs. In this paper we investigate to what extent such a principle holds for quantum algorithms. We propose two natural candidate quantum Yao principles, a "weak" and a "strong" one. For both principles, we prove that the quantum bounded-error complexityis a lower bound on the quantum analogues of max碌 D驴碌 (f). We then prove that equality cannot be obtained for the "strong" version, by exhibiting an exponential gap. On the other hand, as a positive result we prove that the "weak" version holds up to a constant factor for the query complexity of all symmetric Boolean functions.