The Foundational Questions Institute (FQXi) awards grants to “catalyze, support, and disseminate research on questions at the foundations of physics and cosmology”. The grant awarded to Emerson and his collaborators was one of 37 applications selected for funding this year from a total of 211 initial applications that were submitted by institutions, universities, colleges, laboratories, think tanks and businesses from around the world.
The proposed experiment will apply neutron interferometry to perform a high-sensitivity test for the presence of new forms of coherence – forms of coherence that are beyond those predicted by standard quantum mechanics. The experiment is equivalent to a three-slit experiment, which is a direct generalization of the usual two-slit experiment that is a well-known means of demonstrating quantum coherence via an interference fringe. The possibility of observing the higher forms of coherence effects predicted by a class of theories belonging to the so-called `generalized probability theories’ framework via a three-slit interference experiment was highlighted in a paper published by Emerson with Cozmin Ududec and Howard Bauman, “Three slit experiments and the structure of quantum theory”, in Foundations of Physics in 2011.
The experiment will study the three-level system of spatially coherent individual neutrons generated using a five-blade neutron interferometer. They will conduct the experiment at the NIST Center for Neutron Research – the group has a dedicated neutron beam break at NIST that they can use for the experiment.
A few three-slit experiments have been done in the past using photons, including experiments performed by the research groups of Gregor Wiehs and Ray Laflamme here at IQC. Performing the experiment with neutrons will broaden the scope of three-slit tests for new physics, as well as offer several technical advantages, such as the absence of any detection efficiency loopholes.