Searching for microscopic classical cats

TL;DR

This paper proposes experiments to test whether photon absorption by atoms can violate quantum superposition, potentially revealing new superselection rules and shedding light on the quantum-to-classical transition.

Contribution

It introduces a novel experimental approach to search for explicit violations of superposition during photon-atom interactions, addressing foundational questions in quantum measurement.

Findings

Potential identification of conditions where superposition may be suppressed

Experimental tests could confirm or refute superposition in photon absorption

Implications for understanding the quantum measurement problem

Abstract

With the exception of superselection rules, there are no known explicit violations of the Principle of quantum Superposition. However, quantum measurement and the emergence of classicality seem to imply that the Principle of Superposition is not universal, so perhaps new superselection rules or something similar wait to be found. This invites us to search for explicit violations of superposition, even in places where we expect it to hold. Given that many quantum measurement devices rely on atoms absorbing photons, these processes are natural places for a first search for such violations. We propose experiments designed to test whether the emission and absorption of photons by atoms may suppress the interference in certain conditions. If the atom is found, in certain situations, to absorb completely the photon, this would mean that in those situations the atom cannot exist or at least it cannot be stable as a superposition of states in which it absorbed the photon and it did not absorb it. Then we will have a new possibility to resolve the problem of measurement, and that of the emergence of classicality. A negative result would mean an additional confirmation of the Principle of Superposition in these particular cases.