The neutron interferometer is a device that uses the quantum mechanical wave-like properties of free neutrons to measure certain properties of matter very precisely. It functions much like a light interferometer, except that it detects the interference of neutron matter waves rather than light waves. A cold neutron (moving less than 2000 m/s) has an associated quantum wavelength comparable in size to the spacing of atoms in a solid, so it interacts with these atoms coherently, i.e. like a matter wave rather than a particle. When a slow neutron enters the interferometer, its matter wave is diffracted in a perfect silicon crystal and splits into two sub-waves, each taking a different path. The two sub-waves meet again in a another crystal and can interfere with each other. The degree of interference determines the probability of detecting the neutron in a neutron detector placed behind the interferometer. We can place a piece of matter, a magnetic or electric field, or even a gravitational field inside the interferometer to shift the phase of one sub-wave relative to another and change this interference. This gives important and often unique information about the strength and nature of the neutron's interaction in the material or field. We use the neutron interferometer to study phenomena important for nuclear physics, such as the internal charge distribution of the neutron and the scattering of neutrons from light nuclei.
Several graduate and undergraduate students participate in this research program. In addition to learning the science of neutron interferometry, they are educated broadly in the physics and methodology of research at neutron sources, which prepares them for a wide range of careers related to neutron science in academia and industry.
