Quantum theory at the macroscopic scale

TL;DR

This paper challenges the traditional view that macroscopic systems are classical by demonstrating that they can retain quantum behavior, violating classical inequalities even under realistic conditions.

Contribution

It shows that macroscopic systems can exhibit quantum properties robustly, contradicting the assumption that classical mechanics naturally emerges at large scales.

Findings

Violation of Bell inequality in macroscopic systems

Violation of Leggett-Garg inequality in macroscopic systems

Quantum behavior persists despite decoherence and coarse measurements

Abstract

The quantum description of the microscopic world is incompatible with the classical description of the macroscopic world, both mathematically and conceptually. Nevertheless, it is generally accepted that classical mechanics emerges from quantum mechanics in the macroscopic limit. In this letter, we challenge this perspective and demonstrate that the behavior of a macroscopic system can retain all aspects of the quantum formalism, in a way that is robust against decoherence, particle losses and coarse-grained (imprecise) measurements. This departure from the expected classical description of macroscopic systems is not merely mathematical but also conceptual, as we show by the explicit violation of a Bell inequality and a Leggett-Garg inequality.