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Decoherence in the Electron-Wall System
Decoherence theory is often considered to be an important step towards a complete explanation of the quantum to classical transition. Reducing decoherence has been essential for developing quantum computing devices. It has been proposed that understanding decoherence mechanisms in electron microscopes may help to reach the diffraction limit and thus improve the imaging resolution. Dephasing is sometimes confused for, but different from, decoherence. It is a reversible phenomenon while decoherence is irreversible. Entropy is thus a useful measure to distinguish them. However, in most experiments, obtaining all the information needed to determine the entropy is difficult, expensive, or even impossible. We propose an alternative method to distinguish between dephasing and decoherence for the purpose of designing future electron-wall experiments. The electron-wall system is designed to study single electron decoherence for an electron ﬂying above and parallel to a surface. When experimenting with a semiconductor wall (copper oxide), charging due to secondary emission is found to dephase the electron wave in the regime where different decoherence theories predict decoherence. When experimenting with GaAs the conductivity can be changed with laser illumination. Conductivity associated with Joule heating is the relevant parameter for electron-wall decoherence theories. This leads to the hope that by switching from a conductive to an insulating surface, one can turn on and off decoherence. We found strong surface photovoltage eﬀects with super-bandgap and sub-bandgap laser illumination. These eﬀects are explained by detailed carrier dynamics in both situations and their ﬁelds dephase the electron wave. Decoherence theories related to Joule heating are at odds with this experiment, which is puzzling. On the other hand, the understanding of these dephasing eﬀects may lead to pathways that reduce their eﬀects and hopefully reveal electron-wall decoherence.
Chen, Zilin, "Decoherence in the Electron-Wall System" (2021). ETD collection for University of Nebraska - Lincoln. AAI28490058.