Obstructions to Bell CMB Experiments

Abstract

We present a general and systematic study of how a Bell experiment on the cosmic microwave background could be carried out. We introduce different classes of pseudo-spin operators and show that, if the system is placed in a two-mode squeezed state as inflation predicts, they all lead to a violation of the Bell inequality. However, we also discuss the obstacles that one faces in order to realize this program in practice and show that they are probably insurmountable. We suggest alternative methods that would reveal the quantum origin of cosmological structures without relying on Bell experiments.

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References in corpus (6)

• Cosmic Bell Test: Measurement Settings from Milky Way Stars
• Bell violation in the Sky
• Decoherence in the cosmic background radiation
• Classicalization of inflationary perturbations by collapse models in the light of BICEP2
• Verification of quantum discord
• No-activation theorem for Gaussian nonclassical correlations by Gaussian operations

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