Physics of Confined Electrons and Electron Spins on Liquid Helium

Princeton University, Princeton NJ

Investigators

Abstract

****NON-TECHNICAL ABSTRACT**** Electrons are a fundamental constituent of all atoms, and it is the tremendous variety of forms their interactions can take that is largely responsible for the wide range of material properties we see in the world around us. This experimental project is aimed at understanding more about the ways in which interactions between electrons manifest themselves. The motion and states of the electrons are governed by quantum mechanics, but under special circumstances classical Newtonian physics provides a good approximation to their behavior. In one set of experiments a small number of electrons will gradually be forced closer and closer together to increase the importance of quantum mechanical effects, and to understand how that affects their interactions. In addition to having a negative electric charge, every electron also acts like an extremely weak bar magnet. Another set of experiments will study how these "magnetic moments" interact as the electrons are brought together. An important aim of this part of the project is to develop a way to measure the orientation of the magnetic moment of a single electron. Demonstrating this capability represents an important step towards constructing a quantum computer that uses the magnetic moments of individual electrons as its bits. This project will support the education of a Ph.D. student, together with the participation of undergraduate researchers, working at the boundary between fundamental physics and its applications to new technological opportunities. These students will learn how to use the most advanced tools of modern nanoscience research, which has proven to be excellent training for careers in both academia and high technology industries. ****TECHNICAL ABSTRACT**** This individual investigator award supports a project that will use electrons floating on the surface of superfluid helium to study the onset of quantum effects in electron-electron interactions and spin relaxation and decoherence in quantum dot structures. Submicron structures (dots) will be developed to tightly confine electrons on the helium in small clusters, and the energy to successively add electrons will be measured. These experiments will take advantage of recent developments in reliably moving individual electrons across the helium surface to measure electrons outside the dot, rather than within the dot where the sensing structures distort the potentials. The total energy in similar dot structures with two trapped electrons will depend upon their relative spins, with singlet states lying lower than triplets. Measurements of the achievable singlet-triplet splitting will be made, and structures optimized for large splitting. By careful study of the time scales over which particular spin states persist it is expected to be able to determine the electron spin relaxation and decoherence times. The ability to measure single electron spins and their decoherence are key steps on the road to implementing an electron spin quantum computer. This research will be performed by a Ph.D. student and part-time undergraduate students. The students will learn nanofabrication, low-temperature techniques, and high-sensitivity measurements on the experimental end, and about the theory of many-body quantum systems and quantum information. These skills, requiring resourcefulness and attention to detail have proven themselves to be excellent training for scientific careers in academia and high technology industries.