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Coherent control of free electrons
Quantum mechanics has revolutionized our understanding of the world that surrounds us. Quantum mechanical theory, which is over 100 years old is still being pushed to its limits and has found its way into our everyday lives through advanced technologies. A fundamental feature of quantum mechanics is the coherent behavior of matter waves. For one of the most accessible particles; the electron, fully coherent controllable wave packets propagating in free space have not been realized. Applications and also quantum mechanical tests would benefit tremendously from the capability to fully control both the spatial and temporal properties of an electron packet. ^ To investigate the limits of spatial coherence we have experimentally obtained diffraction limited free electron beams (coherent spatial control) and have used these well controlled beams to study electron diffraction from metal coated nano-fabricated gratings. We described our electron diffraction from nano-fabricated gratings with a path integral formulation of quantum mechanics, which fits well with our observed data. In the pursuit of temporal coherence we have created ultrashort electron pulses from a field emission tip by irradiating it with laser pulses from a femtosecond oscillator. This has allowed us to create and study electron pulses with durations less than 100 femtoseconds, which may lead to the development of diffraction limited temporal electron packets (coherent temporal control). Investigating and understanding the exact emission mechanism(s) may allow operation of this source at the fastest controlled timescales currently possible; the sub-cycle/attosecond regime. ^ By using either or both the spatial and temporal electron control, fundamental quantum mechanical tests can be pushed to their limits. Time resolved decoherence, the Pauli Exclusion Principle, and the Aharonov-Bohm effect can all be tested. Applications of spatial and temporal electron control are found in Ultrafast Electron Microscopy, where the spatial and temporal diffraction limit has not yet been reached. This ultrafast coherent control of electrons may allow images to be captured of the electron motion in atoms and molecules. This fundamental advancement would increase our understanding about the basic building blocks of nature.^
Barwick, Brett E, "Coherent control of free electrons" (2007). ETD collection for University of Nebraska - Lincoln. AAI3252443.