Polynomial degree vs. quantum query complexity

  • Authors:
  • Andris Ambainis

  • Affiliations:
  • Department of Combinatorics and Optimization and Institute for Quantum Computing, University of Waterloo, 200 University Avenue West, Waterloo, Ont. N2L 3G1, Canada

  • Venue:
  • Journal of Computer and System Sciences - Special issue on FOCS 2003
  • Year:
  • 2006

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Abstract

The degree of a polynomial representing (or approximating) a function f is a lower bound for the quantum query complexity of f. This observation has been a source of many lower bounds on quantum algorithms. It has been an open problem whether this lower bound is tight. We exhibit a function with polynomial degree M and quantum query complexity @W(M^1^.^3^2^1^...). This is the first superlinear separation between polynomial degree and quantum query complexity. The lower bound is shown by a generalized version of the quantum adversary method.