Ruling Out Multi-Order Interference in Quantum Mechanics
Urbasi Sinha,1,* Christophe Couteau,1,2 Thomas Jennewein,1 Raymond Laflamme,1,3 Gregor Weihs1,4,*
Quantum mechanics and gravitation are two pillars of modern physics. Despite their success in describing the physical world around us, they seem to be incompatible theories. There are suggestions that one of these theories must be generalized to achieve unification. For example, Born’s rule—one of the axioms of quantum mechanics—could be violated. Born’s rule predicts that quantum interference, as shown by a double-slit diffraction experiment, occurs from pairs of paths. A generalized version of quantum mechanics might allow multipath (i.e., higher-order) interference, thus leading to a deviation from the theory. We performed a three-slit experiment with photons and bounded the magnitude of three-path interference to less than 10–2 of the expected two-path interference,thus ruling out third- and higher-order interference and providinga bound on the accuracy of Born’s rule. Our experimentis consistent with the postulate both in semiclassical and quantumregimes.
1 Institute for Quantum Computing and Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada. 2 Laboratoire de Nanotechnologie et d’Instrumentation Optique, Université de Technologie de Troyes, 12 rue Marie Curie, 10 000 Troyes, France. 3 Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, Ontario N2L 2Y5, Canada. 4 Institut für Experimentalphysik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.