From optimal measurement to efficient quantum algorithms for the hidden subgroup problem over semidirect product groups

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

  • Affiliations:
  • Department of Computer Science & Engineering University of Washington, Seattle, WA;Institute for Quantum Information, California Institute of Technology, Pasadena, CA;!Department of Computer Science and Department of Physics, University of California, Santa Barbara, Santa Barbara, CA

  • Venue:
  • FOCS '05 Proceedings of the 46th Annual IEEE Symposium on Foundations of Computer Science
  • Year:
  • 2005

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Abstract

We approach the hidden subgroup problem by performing the so-called pretty good measurement on hidden subgroup states. For various groups that can be expressed as the semidirect product of an abelian group and a cyclic group, we show that the pretty good measurement is optimal and that its probability of success and unitary implementation are closely related to an average-case algebraic problem. By solving this problem, we find efficient quantum algorithms for a number of nonabelian hidden subgroup problems, including some for which no efficient algorithm was previously known: certain metacyclic groups as well as all groups of the form Z^r _p xZp for fixed r (including the Heisenberg group, r = 2). In particular, our results show that entangled measurements across multiple copies of hidden subgroup states can be useful for efficiently solving the nonabelian HSP.