The Quantum Neutron
Dmitry Pushin
The neutron, one of the most common building blocks of matter, is also a unique probe for studying materials and fundamental interactions. The only electrically-neutral nucleus, the neutron passes through most materials with ease, even at the lowest energies. Nowadays neutrons, even with their ~ 15 minute lifetime, are used to study problems ranging from charging and discharging of common batteries to cosmological dark energy. Here I will focus on the neutron as a quantum particle. We use a Mach-Zehnder neutron interferometer to place a neutron into superposition states separated by decimeters, and exploit quantum interference for searches of dark energy and to characterize materials. In particular we show the use of quantum information concepts to enhance coherence, and exploit new degrees of freedom such as orbital and spin/orbit twists of neutron waves.