2020/10/05 by Yunchao Liu, Srinivasan Arunachalam, Kristan Temme · 1 voice · 5 citations
Computer Science · Physics and Astronomy · #cs.LG #quant-ph
paper · pdf · doi:10.1038/s41567-021-01287-z
published as Nature Physics, 2021 · 27 pages, 2 figures
arxiv published 2020/10/05 · arxiv created 2020/11/30 · arxiv updated 2021/07/14
Over the past few years several quantum machine learning algorithms were proposed that promise quantum speed-ups over their classical counterparts. Most of these learning algorithms either assume quantum access to data -- making it unclear if quantum speed-ups still exist without making these strong assumptions, or are heuristic in nature with no provable advantage over classical algorithms. In this paper, we establish a rigorous quantum speed-up for supervised classification using a general-purpose quantum learning algorithm that only requires classical access to data. Our quantum classifier is a conventional support vector machine that uses a fault-tolerant quantum computer to estimate a kernel function. Data samples are mapped to a quantum feature space and the kernel entries can be estimated as the transition amplitude of a quantum circuit. We construct a family of datasets and show that no classical learner can classify the data inverse-polynomially better than random guessing, assuming the widely-believed hardness of the discrete logarithm problem. Meanwhile, the quantum classifier achieves high accuracy and is robust against additive errors in the kernel entries that arise from finite sampling statistics.