Ph.D Thesis

Ph.D StudentGantz Liron
SubjectQuantum Bits Utilizing the Quantum Dot Confined Bright
and Dark Excitons
DepartmentDepartment of Electrical and Computers Engineering
Supervisors PROFESSOR EMERITUS Gad Bahir
Full Thesis textFull thesis text - English Version


The physical representation of a quantum bit (qubit) is a two level system. Qubits are the physical building blocks for quantum information processing. Semiconductor quantum dots confine charge carriers into a three dimensional region of nanometer dimensions. A confined electron-hole pair with antiparallel spins is called a bright exciton because of its strong interaction with light. An electron-hole pair parallel spins is called a dark exciton since it interacts very weakly with light due to its mixing with the bright exciton. Both the bright and the dark exciton have two eigenstates and therefore they can be used as qubits. In this thesis we study the dark and bright excitons as matter (anchored) qubits. Together with their respective two excitons (biexciton) levels, they form systems of either three or four optically connected

energy levels with different properties. We study experimentally different optical control schemes of these exciton qubits using their respective biexciton levels. We exploit the AC Stark effect and externally applied magnetic field induced Zeeman splitting in order to control these qubits. Additionally, we study the indistinguishability of photons emitted when these excitons and biexcitons recombine radiatively. Our experimental findings are in agreement with a theoretical model that we developed. Our model takes into account dephasing processes characteristic to these excitonic qubits.