Any AND-OR Formula of Size N can be Evaluated in time N^{1/2 + o(1)} on a Quantum Computer

  • Authors:
  • Andris Ambainis;Andrew M. Childs;Ben W. Reichardt;Robert Spalek;Shengyu Zhang

  • Affiliations:
  • -;-;-;-;-

  • Venue:
  • FOCS '07 Proceedings of the 48th Annual IEEE Symposium on Foundations of Computer Science
  • Year:
  • 2007

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Abstract

For any AND-OR formula of size N, there exists a bounded-error N^{1/2 + o(1)} -time quantum algorithm, based on a discrete-time quantum walk, that evaluates this formula on a black-box input. Balanced, or "approximately balanced," formulas can be evaluated in {\rm O}(\sqrt N ) {\rm O}(\sqrt N ) (2 - o(1))th power of the quantum query complexity is a lower bound on the formula size, almost solving in the positive an open problem posed by Laplante, Lee and Szegedy.