Do Gedankenexperiments compel quantization of gravity?

Abstract

Whether gravity is quantized remains an open question. To shed light on this problem, various Gedankenexperiments have been proposed. One popular example is an interference experiment with a massive system that interacts gravitationally with another distant system, where an apparent paradox arises: even for space-like separation the outcome of the interference experiment depends on actions on the distant system, leading to a violation of either complementarity or no-signalling. A recent resolution shows that the paradox is avoided when quantizing gravitational radiation and including quantum fluctuations of the gravitational field. Here we show that the paradox in question can also be resolved without considering gravitational radiation, relying only on the Planck length as a limit on spatial resolution. Therefore, in contrast to conclusions previously drawn, we find that the necessity for a quantum field theory of gravity does not follow from so far considered Gedankenexperiments of this type. In addition, we point out that in the common realization of the setup the effects are governed by the mass octopole rather than the quadrupole. Our results highlight that no Gedankenexperiment to date compels a quantum field theory of gravity, in contrast to the electromagnetic case.

arXiv comment5 pages, 1 figure

References in corpus (10)

• Hilbert Space Representation of the Minimal Length Uncertainty Relation
• Quantum gravity and minimum length
• Minimal Length Scale Scenarios for Quantum Gravity
• Universality of Quantum Gravity Corrections
• Probing Planck-scale physics with quantum optics
• Quantum Superposition of Massive Objects and the Quantization of Gravity
• Experiments testing macroscopic quantum superpositions must be slow
• Information Content of the Gravitational Field of a Quantum Superposition
• Two-slit diffraction with highly charged particles: Niels Bohr's consistency argument that the electromagnetic field must be quantized
• Introduction to Bronstein's "Quantum theory of weak gravitational fields"

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• Conditions for graviton emission in the recombination of a delocalized mass
• Gravitational entanglement and the mass contribution of internal energy in nonrelativistic quantum systems