Nanoscale quantum transport for quantum information processing
Loading...
Date
2013-04-25T19:21:53Z
Authors
Qassemi Maloomeh, Farzad
Journal Title
Journal ISSN
Volume Title
Publisher
University of Waterloo
Abstract
In this thesis, I study quantum transport of electron (e.g., current and noise) in quantum dots exploring microscopic processes responsible for spin-relaxation in double quantum dots in Pauli spin blockade regime. This is a regime where current is blocked due to the spin configuration of electrons in the dot. The Pauli
spin blockade provides a means for preparation, manipulation and readout in spin qubits. Hence, understanding the underlying mechanism which lifts this blockade is extremely important.
First, I have developed a theory of spin-flip cotunneling (higher order tunneling) processes in double quantum dots in the Pauli spin blockade regime. Utilizing this
theory, I have calculated the full analytical dependence of the stationary current on applied magnetic fields, gate voltages, and an inter-dot tunnel coupling in Pauli
spin blockade. This work is important for understanding the nature of leakage, especially in systems where other spin-flip mechanisms (due, e.g., hyperfine coupling
to nuclear spins or spin-orbit coupling) are weak, including silicon and carbon nanotube or graphene quantum dots. This theory explains recent experiments on
carbon nanotubes and silicon double quantum dot.
In addition, I propose a new scheme based on the current noise to probe spin relaxation mechanisms in double quantum dot in the Pauli spin blockade regime, where spin-selection rule applies. As a result, I provide a simple closed-form expression which can be used to fit experimental data to extract multiple spin-relaxation
rates, even at very low energy splitting. This method allows for the characterization of different aspects of decay process in these systems.
Description
Keywords
Quantum Information, Spintronics