Dmitry A. Pushin

Controlling neutron orbital angular momentum

The quantized orbital angular momentum (OAM) of photons offers an additional degree of freedom and topological protection from noise. Photonic OAM states have therefore been exploited in various applications ranging from studies of quantum entanglement and quantum information science to imaging. The OAM states of electron beams have been shown to be similarly useful, for example in rotating nanoparticles and determining the chirality of crystals. However, although neutrons—as massive, penetrating and neutral particles—are important in materials characterization, quantum information and studies of the foundations of quantum mechanics, OAM control of neutrons has yet to be achieved. Here, we demonstrate OAM control of neutrons using macroscopic spiral phase plates that apply a ‘twist’ to an input neutron beam. The twisted neutron beams are analysed with neutron interferometry. Our techniques, applied to spatially incoherent beams, demonstrate both the addition of quantum angular momenta along the direction of propagation, effected by multiple spiral phase plates, and the conservation of topological charge with respect to uniform phase fluctuations. Neutron-based studies of quantum information science, the foundations of quantum mechanics, and scattering and imaging of magnetic, superconducting and chiral materials have until now been limited to three degrees of freedom: spin, path and energy. The optimization of OAM control, leading to well defined values of OAM, would provide an additional quantized degree of freedom for such studies.

Reciprocal space approaches to neutron imaging

Here the authors introduce a Fourier based method for phase contrast neutron imaging, report its experimental implementation, and show results for a one-dimensional test phantom. This approach makes use of neutron interferometry to achieve both phase contrast and to spatially code the phase of the neutron with a linear phase grating. The spatial information is recovered from the coherent interference of this phase grating and a spatial phase distribution due to the sample. By moving neutron imaging from real to reciprocal space they avoid the need for position sensitive detectors and improve the potential image resolution.

Broadband Neutron Interferometer

We demonstrate a two phase-grating, multi-beam neutron interferometer by using a modified Ronchi setup in a far-field regime. The functionality of the interferometer is based on the universal moiré effect that was recently implemented for X-ray phase-contrast imaging in the far-field regime. Interference fringes were achieved with monochromatic, bichromatic, and polychromatic neutron beams; for both continuous and pulsed beams. This far-field neutron interferometry allows for the utilization of the full neutron flux for precise measurements of potential gradients, and expands neutron phase-contrast imaging techniques to more intense polycromatic neutron beams. ∗ dmitry.pushin@uwaterloo.ca † Also at Institute for Quantum Computing, University of Waterloo, Waterloo, ON, Canada, N2L3G1 ‡ Also at Department of Chemistry, University of Waterloo, Waterloo, ON, Canada, N2L3G1; Also at Perimeter Institute for Theoretical Physics, Waterloo, ON, Canada, N2L2Y5; Also at Canadian Institute for Advanced Research, Toronto, Ontario, Canada, M5G1Z8

Design of remnant magnetization FeCoV films as compact, heatless neutron spin rotators

We introduce a design of a neutron spin rotator for applications with space and temperature constraints. These passive devices employ remnant magnetization FeCoV thin films and can be tuned experimentally to achieve arbitrary rotation of an incident neutron with a known spin state. Polarized neutron reflectometry measurements are reported for FeCoV monolayer films at thicknesses of 0.5 μm and 5.3 μm to characterize the depth-dependent vector magnetization in the films. Results for a prototype set of film rotators are presented, and the stray field near such films is characterized.