Quantum Fourier sampling simplified

We isolate and generalize a technique implicit in many quantum algorithms, including Shor’s algorithms for factoring and discrete log. In particular, we show that the distribution sampled after a Fourier transform over Zp can be efficiently approximated by transforming over Z, for any q in a large range. Our result places no restrictions on the superposition to be transformed, generalizing previous applications. In addition, our proof easily generalizes to multi-dimensional transforms for any constant number of dimensions.