Electron Spins on Liquid Helium for Quantum Computing

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The continuing advance in the performance of conventional computers is approaching some difficult fundamental barriers. Quantum computing is a new model for information processing, which promises performance beyond that possible for any conventional computer, at least for certain problems. However, quantum computers are very difficult to build. They require precise control over the interactions amongst a large group of small quantum systems while preventing them from interacting with anything else in their environment. The magnetic moments (spins) of electrons are promising candidates for small quantum systems since they naturally interact only weakly with their environment. Conventional electronic devices operate by controlling the motion of electrons, and it may be possible to harness this ability to control the interactions between the electrons' spins. However, instead of the thousands or millions of electrons which are used in conventional electronic devices, quantum computers must be engineered to control each individual electron.This research involves controlling electrons floating in a vacuum about10nm above the surface of superfluid liquid helium. It has been predicted that under these conditions the spin coherence will be long much longer than when the electrons are moving in a solid as in conventional electronic devices. Ensemble pulsed electron spin resonance measurements will be conducted to measure the electrons' spin coherence, or at least to put a lower limit on the coherence time. Experimental work has already shown that packets with 100 or fewer electrons can be reliably moved across the surface of the helium. Experiments will be performed to isolate, move, and measure individual electrons on the helium surface. The students working on this project will learn skills to enable them to be productive researchers.