Originally published November 30, 2022 - UW Imprint
For the first time in history, scientists have created a device that recreates the properties of light using neutrons: the neutral subatomic particles found in the nucleus of an atom. This breakthrough provides a new modified platform for researchers to study the development of next-generation quantum materials with applications ranging from quantum computing to identifying and solving new problems in fundamental and applied physics.
Dr. Dmitry Pushin is an associate professor in physics and astronomy at the Institute of Quantum Computing at the University of Waterloo. He and his team of experienced scientists created a device that generates twisted neutrons with well-defined orbital angular momentum. Dr. Dusan Sarenac, a research associate with IQC and technical lead of Transformative Quantum Technologies at the University of Waterloo, better explains the concept. He says, “Neutrons are a powerful probe for the characterization of emerging quantum materials because they have several unique features” and “they have nanometer-sized wavelengths, electrical neutrality, and a relatively large mass.” All these features mean neutrons can effectively pass through materials that X-rays and light cannot.
While methods for the experimental production and analysis of orbital angular momentum in photons and electrons are well-studied, a device design using neutrons has never been demonstrated until now. Due to the neutron’s distinct characteristics, the researchers had to construct new devices and create novel methods for working with them. In their experiments, Pushin and his team constructed microscopic fork-like silicon grating structures. These devices are so minuscule that in an area of only 0.5 cm by 0.5 cm, there are over six million individual fork dislocation phase gratings. As a beam of single neutrons passes through this device, the individual neutrons begin winding in a corkscrew pattern. After travelling 19 meters, an image of the neutrons was captured using a special neutron camera. The group observed that every neutron had expanded to a 10 cm wide donut-like signature. The donut pattern of the propagated neutrons indicates that they have been put in a special helical state and that the group’s grating devices have generated neutron beams with quantized orbital angular momentum, the first experimental achievement of its kind.
The team published a paper on the experimental realization of neutron helical waves in Science Advances. The research was funded through TQT, a Canada First Research Excellence Fund Initiative. Experimental devices were created in the Quantum Nano Fabrication and Characterization Facility at the University of Waterloo.
Dr. Dmitry Pushin uses his broad background to apply quantum information processing methods to improve neutron interferometry to make it accessible to the general scientific community. He explains, “Neutrons have been popular in the experimental verification of fundamental physics, using the three easily accessible degrees of freedom: spin, path and energy.” He also elaborates on the procedure of the experiments; he says, “In these experiments, our group has enabled the use of orbital angular momentum in neutron beams, which will essentially provide an additional quantized degree of freedom. In doing so, we are developing a toolbox to characterize and examine complicated materials needed for the next generation of quantum devices such as quantum simulators and quantum computers.”
