Advantages of multi-copy nonlocality distillation and its application to minimizing communication complexity

TL;DR

This paper introduces new multi-copy nonlocality distillation protocols that enhance nonlocal correlations, with implications for understanding quantum nonlocality limits and reducing communication complexity in quantum information tasks.

Contribution

It presents novel multi-copy distillation schemes, including genuine three-copy protocols, improving the distillation of nonlocal correlations beyond previous methods.

Findings

Genuine three-copy protocols outperform two-copy protocols in certain regions.

New protocols expand the set of nonlocal correlations that can be distilled.

Application of protocols increases regions where nonlocality reduces communication complexity.

Abstract

Nonlocal correlations are a central feature of quantum theory, and understanding why quantum theory has a limited amount of nonlocality is a fundamental problem. Since nonlocality also has technological applications, e.g., for device-independent cryptography, it is useful to understand it as a resource and, in particular, whether and how different types of nonlocality can be interconverted. Here we focus on nonlocality distillation which involves using several copies of a nonlocal resource to generate one with more nonlocality. We introduce several distillation schemes which distil an extended part of the set of nonlocal correlations including quantum correlations. Our schemes are based on a natural set of operational procedures known as wirings that can be applied regardless of the underlying theory. Some are sequential algorithms that repeatedly use a two-copy protocol, while others are genuine three-copy distillation protocols. In some regions we prove that genuine three-copy protocols are strictly better than two-copy protocols. By applying our new protocols we also increase the region in which nonlocal correlations are known to give rise to trivial communication complexity. This brings us closer to an understanding of the sets of nonlocal correlations that can be recovered from information-theoretic principles, which, in turn, enhances our understanding of what is special about quantum theory.