Spin Control in One-Dimensional Quantum Dots

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****TECHNICAL ABSTRACT****The project aims to design and manipulate quantum states of electrons in one-dimensional quantum dots fabricated from carbon nanotubes. Ultrashort carbon nanotubes are experimental representations of a one-dimensional potential well, in which the allowed energy level spacing depends strongly on the length of the nanotube. By coupling a short section of a nanotube to ferromagnetic or superconducting electrodes via tunnel junctions, one can achieve fine control of the electronic quantum states on the nanotube. These quantum states will be studied through conductance and current shot noise measurements, which will depend strongly on the spins of the electrons. This project will support the education of graduate and undergraduate students, who will receive hands-on training in cutting-edge nanofabrication and low-temperature measurement techniques. In addition to exploring the fundamental issues of custom-designing and controlling quantum states of electrons, the results will serve as the basis for development of novel spin-based quantum devices. In particular, the possibility of creating and observing elusive Majorana fermions would have an enormous impact on both the fundamental understanding of physics and the future topological quantum computing technology.****NON-TECHNICAL ABSTRACT****Electrons are elementary particles with an intrinsic quantum property called spin, which can be either "up" or "down". In quantum mechanics, electrons have all the properties of particles with spin, but they also behave as waves. As a consequence of their wave nature, the energies of electrons in a one-dimensional wire can only take certain allowed values - just like the note played on a guitar string depends on the length of the string, the energy of an electron in a quantum wire depends on the length of the wire. This project aims to design and manipulate the energy states and the spins of electrons in short sections of carbon nanotubes. This will be achieved via electrical measurements that will use spin-sensitive configurations of ferromagnetic and superconducting electrodes. This project will support the education of graduate and undergraduate students, who will receive hands-on training in cutting-edge nanofabrication and measurement techniques at temperatures close to absolute zero. In addition to exploring the fundamental physics of custom-designing and controlling quantum states of electrons, the results will serve as the basis for development of novel spin-based quantum devices. The project offers a unique opportunity to create and observe a new state of matter, which would enable the development of fundamentally fault-tolerant quantum computing technology.