Interaction-free measurements with electrons
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Date
2022-10-04
Authors
Turner, Amy
Journal Title
Journal ISSN
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Publisher
University of Oregon
Abstract
Quantum-enhanced electron imaging promises highly efficient, low-damage transmission electron microscopy, transforming high-resolution imaging of samples affected by beam irradiation. One proposed quantum protocol for damage-free imaging is interaction-free measurement. However, this quantum phenomenon had yet to be experimentally realized with electrons. In this dissertation, we demonstrate the first interaction-free measurement with electrons. To realize this quantum protocol with electrons required the development of a novel, free-electron interferometer constructed in a conventional transmission electron microscope. Here we design and create a flexible two-grating electron Mach-Zehnder interferometer with high contrast in discrete outputs. We test this balanced interferometer with equal-intensity paths to map the electrostatic potential around a nanorod and perform quantitative phase imaging of a nanoparticle. We then achieve a quantum-enhanced, counterfactual measurement with electrons - the interaction-free measurement. Comparing this novel electron interferometer to conventional electron holography, which is a well-established technique in electron microscopy, we find that the interferometer is more suitable for electron interaction-free measurements due to the high contrast in discrete outputs. The two-grating interferometer is then optimized for higher efficiency interaction-free measurements by forming a weak interaction probe that decreases the probability of interacting with the sample. The modified configuration more than doubles the interaction-free measurement efficiency of the original balanced interferometer. This body of work not only includes the development of a versatile electron interferometer, capable of a broad scope of measurements, but realizes a fundamental quantum experiment. Achieving the interaction-free measurement with electrons takes us one step closer to developing a functional quantum-enhanced electron microscope.