טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentDon Yaroslav
SubjectThe Optical Activity of the Dark Exciton and its Potential
Use for Generating a Cluster State of Entangled
Photons
DepartmentDepartment of Physics
Supervisor Professor David Gershoni
Full Thesis textFull thesis text - English Version


Abstract

The dark exciton in semiconductors is formed when an electron is promoted from the full valence band to the empty conduction band and, in addition, its spin projection is flipped. Since light does not interact with the electronic spin, in general, this excitation is not expected to decay radiatively, and therefore, it is termed a dark exciton. In practice, however, we discovered experimentally that, in semiconductor quantum dots, the dark exciton does have optical activity, and it can be optically accessed and coherently controlled.

In this thesis we present a simple model which explains this optical activity in terms of the reduced symmetry of a typical self-assembled semiconductor quantum dot.

In addition, we present a detailed model in which the quantum dot-confined dark exciton is used as an entangler for generating a string of entangled photons, or a photonic cluster state. In order to accomplish this much desired feat with high fidelity, it is crucial to be able to model the physical processes involved precisely. We discuss a model and simulations of the temporal evolution of a one-dimensional photonic cluster state produced by a sequence of optical pulses applied to a quantum dot with a dark exciton in it, using Lindblad dynamics.

Our model is favorably compared with recently available experimental results.