Bell scenarios with communication

TL;DR

This paper investigates how allowing communication between parties affects the ability of classical and quantum models to reproduce correlations, providing insights into quantum nonlocality and potential applications in secure information processing.

Contribution

It systematically analyzes the amount and type of communication needed for classical and quantum models to simulate quantum and no-signalling correlations.

Findings

Classical models require varying communication to reproduce quantum correlations.

Quantum models augmented with classical communication can simulate no-signalling correlations.

Different forms of communication (inputs, outputs, messages) have distinct impacts on correlation reproduction.

Abstract

Classical and quantum physics provide fundamentally different predictions about experiments with separate observers that do not communicate, a phenomenon known as quantum nonlocality. This insight is a key element of our present understanding of quantum physics, and also enables a number of information processing protocols with security beyond what is classically attainable. Relaxing the pivotal assumption of no communication leads to new insights into the nature quantum correlations, and may enable new applications where security can be established under less strict assumptions. Here, we study such relaxations where different forms of communication are allowed. We consider communication of inputs, outputs, and of a message between the parties. Using several measures, we study how much communication is required for classical models to reproduce quantum or general no-signalling correlations, as well as how quantum models can be augmented with classical communication to reproduce no-signalling correlations.