Quantum superposition of massive objects and the quantization of gravity

Alessio Belenchia (Corresponding author), Robert Wald (Corresponding author), Flaminia Giacomini, Esteban Castro Ruiz (Corresponding author), Caslav Brukner (Corresponding author), Markus Aspelmeyer (Corresponding author)

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We analyze a Gedankenexperiment previously considered by Mari et al. [Sci. Rep. 6, 22777 (2016).] that involves quantum superpositions of charged and/or massive bodies (“particles”) under the control of the observers, Alice and Bob. In the electromagnetic case, we show that the quantization of electromagnetic radiation (which causes decoherence of Alice’s particle) and vacuum fluctuations of the electromagnetic field (which limits Bob’s ability to localize his particle to better than a charge-radius), both are essential for avoiding apparent paradoxes with causality and complementarity. We then analyze the gravitational version of this Gedankenexperiment. We correct an error in the analysis of Mari et al. [Sci. Rep. 6, 22777 (2016).] and of Baym and Ozawa [Proc. Natl. Acad. Sci. U.S.A. 106, 3035 (2009).], who did not properly account for the conservation of center of mass of an isolated system. We show that the analysis of the gravitational case is in complete parallel with the electromagnetic case, provided that gravitational radiation is quantized and that vacuum fluctuations limit the localization of a particle to no better than a Planck length. This provides support for the view that (linearized) gravity should have a quantum field description.
Original languageEnglish
Article number126009
Number of pages9
JournalPhysical Review D
Issue number12
Publication statusPublished - 18 Dec 2018

Austrian Fields of Science 2012

  • 103025 Quantum mechanics
  • 103012 High energy physics
  • 103028 Theory of relativity



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