Arbitrarily little knowledge can give a quantum advantage for nonlocal tasks

Abstract

It has previously been shown that quantum nonlocality offers no benefit over classical correlations for performing a distributed task known as nonlocal computation. This is where separated parties must compute the value of a function without individually learning anything about the inputs. We show that giving the parties some knowledge of the inputs, however small, is sufficient to ``unlock'' the power of quantum mechanics to outperform classical mechanics. This role of information held locally gives insight into the general question of when quantum nonlocality gives an advantage over classical physics. Our results also reveal an interesting feature of the nonlocality embodied in the celebrated task of Clauser, Horne, Shimony, and Holt.