Strong nonlocality: A trade-off between states and measurements

TL;DR

This paper explores the theoretical implications of violating Tsirelson's bound by analyzing a model called 'box world' that permits arbitrary nonlocal correlations, revealing limitations in measurement capabilities and the absence of certain quantum information protocols.

Contribution

It introduces and analyzes 'box world', a model with unrestricted nonlocal correlations, highlighting the trade-offs between entanglement and measurement capabilities.

Findings

Box world allows more highly entangled states than quantum theory.

Measurements in box world are limited, preventing entanglement swapping, teleportation, or dense coding.

Abstract

Measurements on entangled quantum states can produce outcomes that are nonlocally correlated. But according to Tsirelson's theorem, there is a quantitative limit on quantum nonlocality. It is interesting to explore what would happen if Tsirelson's bound were violated. To this end, we consider a model that allows arbitrary nonlocal correlations, colloquially referred to as "box world". We show that while box world allows more highly entangled states than quantum theory, measurements in box world are rather limited. As a consequence there is no entanglement swapping, teleportation or dense coding.