New methods to produce and detect optical and matter-wave spin-orbit states

Monday, October 29, 2018

Researchers at the Institute for Quantum Computing (IQC) in collaboration with researchers at the National Institute for Standards and Technology (NIST) have developed a highly robust method for structuring light and matter waves, enhancing the powerful probing ability of neutrons.

Controlling a property of light called Orbital Angular Momentum (OAM) has led to applications in communication, microscopy and manipulating quantum information. Recently, in two different studies, IQC researchers demonstrated a new method of structuring spin-coupled OAM that is more robust and offers new approaches to the study of magnetic and chiral materials.

In the first study, the researchers created a beam of light consisting of a lattice of spin-coupled OAM states. It is the first time that this technique has been applied to optics. To produce the spin-coupled OAM states of light, the researchers used coherent averaging and spatial control methods borrowed from nuclear magnetic resonance.

“Spin-coupled OAM states of light have been used in numerous applications such as achieving extremely high bandwidth data transmission,” explained Dusan Sarenac, technical lead for Transformative Quantum Technologies (TQT). “An enabling feature of our method would be to expand the capability of these beams by providing an array of such states, made available by the lattice structuring.”

The method is extendable to other mediums, such as neutrons. Neutrons are a powerful probe of materials with unique penetrating abilities and magnetic sensitivity, and are particularly powerful for characterizing the inner magnetic field structure of materials because they easily penetrate through materials that normally block light.

Extending the OAM  structuring method to neutrons enhances their powerful probing ability and adds a new degree of freedom for material characterization with neutrons.

“The technique we introduce enables the neutrons to be used as a probe of new types of topological materials whose inner magnetic fields form helices,” said Sarenac, lead author on the paper. “It could lead to exciting advances in neutron optics and neutron imaging.”

A new characterization method for neutrons was also introduced. The method can directly measure the correlations of spin state and transverse momentum, overcoming the major challenge associated with neutrons—low flux and small spatial coherence length.

“The hope is that this detection procedure can be extended to other probes such as electrons and X-Rays,” said Sarenac.

This research was undertaken thanks in part to funding from the Canada First Research Excellence Fund.