qspd 1.0

Quantum Signal Processing Decomposition

This package implements Jeongwan Haah's algorithm for quantum signal processing as described in this paper. It includes a step by step algorithm that decomposes periodic functions (often from quantum signal processing) into a product of primitive matrices, represented as a list of angles. The algorithmic complexity is O(N³ polylog(N/𝜺)) where N is the degree of the periodic function and 𝜺 is the precision parameter. The runtime bottleneck is a polynomial rootfinding in step 2. Haah concludes that the error is at most the error input (=15𝜺). DISCLAIMER: This is in initial investigation stages, and the usage is subject to change.