Signifying the Schrodinger cat in the context of testing macroscopic realism

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.

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• Leggett-Garg tests of macro-realism for multi-particle systems including double-well Bose-Einstein condensates
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• Quantifying the mesoscopic nature of the Einstein-Podolsky-Rosen nonlocality
• Protected cat states from kinetic driving of a boson gas
• Mesoscopic and macroscopic quantum correlations in photonic, atomic and optomechanical systems
• Weak versus deterministic macroscopic realism, and Einstein-Podolsky-Rosen's elements of reality
• Do quantum propositions obey the principle of excluded middle?
• Overturning negative construal of quantum superposition