Quantum theory at the macroscopic scale

21.08.2025

Our paper has been published in: Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences

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 paper,
we challenge this perspective and demonstrate that the behaviour 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.

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