neutrons

By cleverly manipulating two properties of a neutron beam, scientists at the National Institute of Standards and Technology (NIST) and their collaborators have created a powerful probe of materials that have complex and twisted magnetic structures.Penetrating deep inside heavyweight materials, yet still able to interact strongly with light elements, neutron beams image hydrogen-bearing liquids in engine parts, storage tanks and fuel cells. The beams can also map the shapes of polymers on the molecular scale, reveal the precise arrangement of atoms in a crystal and chart the distribution of water within growing plants. Neutron beams became even stronger probes when scientists learned how to harness two quantum properties of the beams. One of these properties, formally known as orbital angular momentum, or OAM, refers to the twisting, or rotational motion of a neutron as it travels forward, similar to the whirlpool formed by water as it travels down a drain. The other quantum property, spin, is related to the neutron’s magnetic field, and can be likened to the spinning motion of a top.

 It’s easy to contemplate the wave nature of light in common experience.  White light passing through a prism spreads out into constituent colors; it diffracts from atmospheric moisture into a rainbow; light passing across a sharp edge or a diffraction grating creates an interference pattern.  It’s harder to fathom the wave behavior of things usually thought of as particles, such as electrons and atoms.  And yet these matter waves play a role in physics and in technology.  For example, electron beams, manifested as waves, provide an important form of microscopy.
Neutrons, a basic constituent of atomic nuclei, have wave properties which are employed in a variety of research areas such as determining the structure of materials.  A recent experiment provides a new handle for control of neutrons by demonstrating that a quantum variable called orbital angular momentum is accessible in beams of neutron waves, and that it can be manipulated for use in neutron imaging and quantum information processing.