Gravity-induced wave-function collapse and experimental tests

• Applicant: Dr. André Großardt
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: from 2014 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 266142017

• Final Report Year: 2017

Final Report Abstract

Whether or not the gravitational field must be described by a quantum theory, similar to the other three fundamental interactions, or behaves differently—in a fundamentally classical way—at the microscopic level, is still an unresolved question. The research project “Gravity-induced wave-function collapse and experimental tests” aimed at studying experimentally testable consequences of the second possibility, and the potential connection of this possibility to another big unresolved question of fundamental physics: how the “collapse” of quantum wave-functions occurs, or how our classical world emerges from the principles of quantum physics. The subject of these studies is the so-called Schrödinger-Newton equation, a nonlinear modification of the Schrödinger equation which describes the evolution of a quantum wave-function, but also contains a term that corresponds to the wave-function attracting itself due to gravitational influences. In the course of this research project, in collaboration with experimental physicists at the University of Southampton, a new effect was found, that due to this gravitational self-influence the energy spectrum of a particle trapped in an electromagnetic field will be distorted. This effect promises to provide a more feasible way to test the Schrödinger-Newton equation than previous proposals. Further outcomes of the project are a more efficient way of calculating the time evolution of a free particle which is subject to a gravitational self-interaction, which could turn out to be helpful for the design of experimental tests in a satellite mission, as well as a better understanding of the difficulties arising when trying to incorporate the Schrödinger-Newton equation into the physics of a specific class of heavy elementary particles, so-called neutral mesons. Research is still ongoing on links of the Schrödinger-Newton equation to the equations that describe light propagating through an optical fibre, which may result in fruitful new insights about both the gravitational and the optical systems.

Publications

• Newtonian self-gravitation in the neutral meson system. Phys. Rev. D, 91, 064056 (2015)
  Großardt, André & Hiesmayr, Beatrix C.
  
• Approximations for the free evolution of self-gravitating quantum particles. Phys. Rev. A, 94, 022101 (2016)
  Großardt, André
  
• Effects of Newtonian gravitational self-interaction in harmonically trapped quantum systems. Sci. Rep., 6, 30840 (2016)
  Großardt, André; Bateman, James; Ulbricht, Hendrik & Bassi, Angelo
  
• Optomechanical test of the Schrödinger– Newton equation. Phys. Rev. D, 93, 096003 (2016)
  Großardt, André; Bateman, James; Ulbricht, Hendrik & Bassi, Angelo
  
• (2017) Gravitational decoherence. Class. Quantum Grav. (Classical and Quantum Gravity) 34 (19) 193002
  Bassi, Angelo; Großardt, André & Ulbricht, Hendrik