Coherent control of neutron interferometry

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, February 2007.Includes bibliographical references (leaves 125-128).In this thesis, several novel techniques are proposed and demonstrated for measuring the coherent properties of materials and testing aspects of quantum information processing using a single crystal neutron interferometer. In particular we introduce methods for reciprocal space encoding of spatial information systematically in a neutron interferometer. First, a proof of principle experiment is conducted for coherent reciprocal space neutron imaging. This newly proposed technique overcomes the limitation of spacial resolution of current two dimensional neutron detectors. Second, an experiment to measure the vertical coherent length of a neutron interferometer is reported, which extends the previously achieved path separation. Third, we propose a new interferometry geometry that reduces the sensitivity of the neutron interferometer to environmental vibrational disturbances. The method is based on a quantum error compensating algorithm. Finally, a new method that is capable of measuring the autocorrelation function of a sample is proposed. This new technique can extend the capability of traditional neutron scattering experiments. All experiments are conducted at the neutron interferometry facility at the National Institute of Standards and Technology (NIST).by Dmitry A. Pushin.Ph.D

Quantum correlations in a noisy neutron interferometer

We investigate quantum coherences in the presence of noise by entangling the spin and path degrees of freedom of the output neutron beam from a noisy three-blade perfect crystal neutron interferometer. We find that in the presence of dephasing noise on the path degree of freedom the entanglement of the output state reduces to zero, however the quantum discord remains non-zero for all noise values. Hence even in the presence of strong phase noise non-classical correlations persist between the spin and path of the neutron beam. This indicates that measurements performed on the spin of the neutron beam will induce a disturbance on the path state. We calculate the effect of the spin measurement by observing the changes in the observed contrast of the interferometer for an output beam post-selected on a given spin state. In doing so we demonstrate that these measurements allow us to implement a quantum eraser, and a which-way measurement of the path taken by the neutron through the interferometer. While strong phase noise removes the quantum eraser, the spin-filtered which-way measurement is robust to phase noise. We experimentally demonstrate this disturbance by comparing the contrasts of the output beam with and without spin measurements of three neutron interferometers with varying noise strengths. This demonstrates that even in the presence of noise that suppresses path coherence and spin-path entanglement, a neutron interferometer still exhibits uniquely quantum behaviour.Comment: 10 pages, 5 figures. V3 includes expanded theoretical analysis and discussion of post-selected spin measurements in different base

Plants with genetically encoded autoluminescence

Autoluminescent plants engineered to express a bacterial bioluminescence gene cluster in plastids have not been widely adopted because of low light output. We engineered tobacco plants with a fungal bioluminescence system that converts caffeic acid (present in all plants) into luciferin and report self-sustained luminescence that is visible to the naked eye. Our findings could underpin development of a suite of imaging tools for plants

Visualization 1: Holography with a neutron interferometer

The intensity profile of Fig. 2 (b) as a continuous function of the topological charge q. Originally published in Optics Express on 03 October 2016 (oe-24-20-22528

Visualization 3: Holography with a neutron interferometer

The two-dimensional phase profile of Fig. 4 with the overall phase in the reconstruction plane varied Originally published in Optics Express on 03 October 2016 (oe-24-20-22528