Quantum Information Enabled Neutron Interferometry

Abstract

Neutron interferometry with its ability to encode and extract information provides a test bed for quantum mechanics and precise measurement of physical quantities of significant importance in physics. However, this significant key investigative technique is weakened by its very fragile nature; neutron interferometry has proven to be highly sensitive to environmental noise.

Once brought to its optimal state, the use of neutron interferometry enabled with quantum information, represents a milestone. Indeed a realization of high-quality neutron interferometry could pave a way to probe materials research such as probing properties water in proteins and topological materials. Thus understanding and solving the sensitivity of neutron interferometers to noise is a key step toward possible applications. This is the core of the work done in this Thesis.

We incorporated two theoretical techniques developed for quantum information sciences into the construction of a new polarized neutron interferometry beam line: The technique of quantum error correction and the technique of open quantum system. One focus of this work is to report on the design, the construction as well as the characteristic features of this beamline.

This thesis involves experimental data, showing how the neutron beam intensity at the exit of a three-blade neutron interferometer can be controlled by the interferometer blades thickness. Secondly, is also presents an alternative and simplified quantum information approach to dynamical diffraction, based on repeated application of a coherent beam- splitting unitary at coarse-grained lattice sites. Demanding translational invariance added to a computationally tractable number of sites in the coarse-graining reproduced many results typical of standard dynamical diffraction theory and experiments. Building on that, a proposal for a new five-blade neutron interferometer is presented and its robustness to noise, resulting from dynamical diffraction together with low-frequency external mechanical vibration is discussed.

Steps ahead in our work, neutron interferometry may be improved as well as adapted to more applications by incorporating the spin and orbital degrees of freedom to a path-based ivinterferometer. In this concern, we propose a method to prepare the spin-orbit state by passing a polarized neutron beam through a quadrupole magnetic field. Initially designed for a beam the size of a coherent length, we extend this method to work for spatially displaced beams by using linear magnetic gradients.