Figure 2: (a) Schematic diagram of the neutron paths in a perfect single crystal neutron interferometer. The neutron passing through the interferometer is coherently split into two paths (upper and lower) by the first interferometer blade, redirected by the middle blades (these blades represent mirrors of the light Mach-Zehnder interferometer and are recombined to observe interference effects by the last blade). The neutron’s wave function can be described as superposition of the paths inside the interferometer. (b) Pictures of NIST interferometers with high contrast (>75%).