Weak Classicality in Coupled N-Level Quantum Systems

TL;DR

This paper explores the concept of weak classicality in large N-level quantum systems, showing that apparent classical behavior arises from limited experimental resources despite persistent non-locality and entanglement.

Contribution

It introduces the notion of weak classical limit and reconciles classicality with non-local quantum features in large N systems.

Findings

Classicality is linked to experimental limitations, not inherent system properties.

Non-locality persists even as N approaches infinity.

Bell-CHSH and CGLMP inequalities are analyzed for N-level systems.

Abstract

The notion of `weak classical limit' for coupled N-level quantum systems as N -> infinity is introduced to understand the precise sense in which one attains classicality. There exist proofs that a system becomes classical at large N. On the other hand, it is known that non-locality and entanglement, the two hallmarks of non-classicality, thrive even as N -> infinity. We reconcile these results in this paper by showing that so called classicality is not so much an inherent property of the system, as it is a consequence of limited experimental resources. Our focus is largely on non-locality, for which we study the Bell-CHSH and CGLMP inequalities for N-level systems.