Quantum algorithm for a generalized hidden shift problem

  • Authors:
  • Andrew M. Childs;Wim van Dam

  • Affiliations:
  • Institute for Quantum Information, California Institute of Technology, Pasadena, CA;University of California, Santa Barbara, Santa Barbara, CA

  • Venue:
  • SODA '07 Proceedings of the eighteenth annual ACM-SIAM symposium on Discrete algorithms
  • Year:
  • 2007

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Abstract

Consider the following generalized hidden shift problem: given a function f on {0,..., M - 1} x ZN promised to be injective for fixed b and satisfying f(b, x) = f(b + 1,x + s) for b = 0, 1,..., M - 2, find the unknown shift s ε ZN. For M = N, this problem is an instance of the abelian hidden subgroup problem, which can be solved efficiently on a quantum computer, whereas for M = 2, it is equivalent to the dihedral hidden subgroup problem, for which no efficient algorithm is known. For any fixed positive ε, we give an efficient (i.e., poly(log N)) quantum algorithm for this problem provided M ≥ Nε. The algorithm is based on the "pretty good measurement" and uses H. Lenstra's (classical) algorithm for integer programming as a subroutine.