It is well known that quantum computers can efficiently find a hidden subgroup
H of a finite Abelian group
G. This implies that after only a polynomial (in
log∣G∣) number of calls to the oracle function, the states corresponding to different candidate subgroups have exponentially small inner product. We show that this is true for noncommutative groups also. We present a quantum algorithm which identifies a hidden subgroup of an arbitrary finite group
G in only a linear (in
log∣G∣) number of calls to the oracle function. This is exponentially better than the best classical algorithm. However our quantum algorithm requires an exponential amount of time, as in the classical case.
The hidden subgroup problem (HSP) plays an important role in quantum computation, because many quantum algorithms that are exponentially faster than classical algorithms can be casted in the HSP structure. In this paper, we present a new polynomial-time quantum algorithm that solves the HSP over the group
Zpr⋊Zqs, when $p^r/q= \up{poly}(\log p^r)$, where
p,
q are any odd prime numbers and
r,s are any positive integers. To find the hidden subgroup, our algorithm uses the abelian quantum Fourier transform and a reduction procedure that simplifies the problem to find cyclic subgroups.