Can gravity account for the emergence of classicality?

Abstract

A recent debate has ensued over the claim by Pikovski et al. [Nat. Phys. 11, 668 (2015)] that systems with internal degrees of freedom undergo a universal, gravity-induced, type of decoherence that explains their quantum-to-classical transition. This decoherence is supposed to arise from the different gravitational redshifts experienced by such systems when placed in a superposition of two wave packets at different heights in a gravitational field. Here we investigate some aspects of the discussion with the aid of simple examples. In particular, we first resolve an apparent conflict between the reported results and the equivalence principle by noting that the static and free-fall descriptions focus on states associated with different hypersurfaces. Next, we emphasize that predictions regarding the observability of interference become relevant only in the context of concrete experimental settings. As a result, we caution against hasty claims of universal validity. Finally, we dispute the claim that, at least in the scenarios discussed by Pikovski et al., gravitation is responsible for the reported results, and we question the alleged ability of decoherence to explain the quantum-to-classical transition. In consequence, we argue against the extraordinary assertion by Pikovski et al. that gravity can account for the emergence of classicality.

10 pages, 6 figures

References in corpus (3)

• Gravitational Decoherence for Mesoscopic Systems
• Comment on "Universal decoherence due to gravitational time dilation"
• Time Dilation in Quantum Systems and Decoherence: Questions and Answers

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• Equivalence Principle for Quantum Systems: Dephasing and Phase Shift of Free-Falling Particles
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• Coupling Quantum Matter and Gravity
• Classical and Nonclassical Time Dilation for Quantum Clocks
• Decoherence due to gravitational time dilation: analysis of competing decoherence effects
• Post-Newtonian corrections to Schrödinger equations in gravitational fields
• General Relativistic Decoherence with Applications to Dark Matter Detection
• Decoherence from General Relativity
• Information transfer during the universal gravitational decoherence
• Semi-classical gravity phenomenology under the causal-conditional quantum measurement prescription
• Post-Newtonian Description of Quantum Systems in Gravitational Fields
• Gravitational entanglement and the mass contribution of internal energy in nonrelativistic quantum systems
• De Broglie relations, Gravitational time dilation and weak equivalence principle