Wavelength-Uniform Quantum Algorithms for Quantum Dynamics

Abstract

One of the main challenges in quantum simulation is the prohibitive cost of computing its solutions in the semi-classical regime, in which the de Broglie wavelength is small compared with the characteristic length scale and the solution is highly oscillatory. This difficulty is overcome by using the Weyl variable, under which the solution is not oscillatory. Furthermore, we use the exact Hermite moments and quantum singular value transformation to treat the polynomial and Fourier components of the potential, resulting in a quantum algorithm efficient for {\it all} ranges of wavelengths. Specifically, it has a {\it polynomial} complexity in spatial dimension, and discretization and query bounds {\it without} negative powers of possibly small wavelength, thus enabling it to capture the correct physical observables even if the spatial grid does not resolve the frequency, hence defying the Nyquist-Shannon sampling theorem.