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

Bacon, Dave; Childs, Andrew M.; van Dam, Wim

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

Authors

Bacon, Dave

Childs, Andrew M.

van Dam, Wim

Description

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_p)^r X| Z_p 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.
18 pages; v2: updated references on optimal measurement