Signifying the Schrodinger cat in the context of testing macroscopic realism

TL;DR

This paper critically examines tests of macroscopic realism using Schrödinger's cat thought experiments, arguing many proposed signatures do not truly negate MR and exploring conditions under which macroscopic local realism could be challenged.

Contribution

It analyzes existing models testing macroscopic realism and introduces a framework for understanding when such tests genuinely challenge the premise.

Findings

Many cat-signatures do not negate MR but can be explained by microscopic effects.

Negating macroscopic local realism may be possible through amplification of quantum noise.

The paper clarifies the assumptions necessary for testing and negating MR and MLR.

Abstract

Macroscopic realism (MR) specifies that where a system can be found in one of two macroscopically distinguishable states (a cat being dead or alive), the system is always predetermined to be in one or other of the two states (prior to measurement). Proposals to test MR generally introduce a second premise to further qualify the meaning of MR. This paper examines two such models, the first where the second premise is that the macroscopically distinguishable states are quantum states (MQS) and the second where the macroscopcially distinguishable states are localised hidden variable states (LMHVS). We point out that in each case in order to negate the model, it is necessary to assume that the predetermined states give microscopic detail for predictions of measurements. Thus, it is argued that many cat-signatures do not negate MR but could be explained by microscopic effects such as a photon-pair nonlocality. Finally, we consider a third model, macroscopic local realism (MLR), where the second premise is that measurements at one location cannot cause an instantaneous macroscopic change to the system at another. By considering amplification of the quantum noise level via a measurement process, we discuss how negation of MLR may be possible.