Experiments presented herein are conducted in two material systems with the single motivation of understanding how to control quantum information. After introducing quantum information, we explain why these two material systems, donor electron spins in silicon and electron spins on the surface of superfluid helium, are strong candidates to become viable qubits, the building blocks of quantum information processing. Our experiments probe the relevant physical structure and demonstrate new techniques for qubit state control.
We measure the Stark shift of 121Sb donor electron spins in silicon using pulsed electron spin resonance at 0.35 T. Interdigitated metal gates on top of an Sb-implanted 28Si epi-layer apply electric fields at donor sites. Two quadratic Stark effects are resolved: a decrease of the hyperfine coupling between electron and nuclear spins of the donor and a decrease in electron Zeeman g-factor. The hyperfine term prevails at our X-band magnetic fields of 0.35T, while the g-factor term is expected to dominate at higher magnetic fields. A significant linear Stark effect is also observed, which we suggest arises from strain. We discuss the results in the context of the Kane model quantum computer, confirming that Stark tuning is a convenient way to change the spin resonance energy of individual electrons, and thus provide addressability using electrostatic gates.
We also measure the transport of surface electrons on liquid helium at 1.5K using micro-fabricated channel devices. The channels, which are filled with superfluid 4He by capillary action, have small underlying metal gates for electron control and detection. Initial studies with simple self-fabricated devices inspired the use of silicon devices for advantages in complexity and advanced processing capabilities. Our silicon device has 120 parallel channels and an intersecting perpendicular channel with 3 µm and 2.5 µm widths, respectively. Connected as in a 3-phase charge coupled device with a period of 3 µm, underlying gates in the parallel and perpendicular channels are shown to transport electrons across billions of pixels with no detectable transfer failures, proving two-dimensional scalability. Further, our results hold for singly occupied channels, paving the way for transporting quantum information carried by the electron spin.
|Advisor:||Lyon, Stephen A.|
|School Location:||United States -- New Jersey|
|Source:||DAI-B 71/11, Dissertation Abstracts International|
|Subjects:||Electrical engineering, Electromagnetics, Condensed matter physics|
|Keywords:||Cold electrons, Electron spins, Electrons on liquid helium, Helium, Quantum information, Silicon, Superfluid|
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