טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentCogan Dan
SubjectTowards Realization of One and Two Dimensional
Photonic Cluster States
DepartmentDepartment of Physics
Supervisor Professor David Gershoni


Abstract

Cluster states of entangled photons are considered to be the fundamental building blocks of innumerous emerging measurement based protocols for quantum computation and communication. In those protocols, the computation and communication are performed simply by single qubit measurements performed on prefabricated cluster states. Generating cluster states in a deterministic manner has become a paramount yet challenging task. Here we demonstrate deterministic generation of a cluster state of entangled photons by repeating excitation of a quantum dot spin. For doing so we develop a method for a single-shot optical initialization of this quantum dot spin to a predetermined state of our choosing. In addition, we develop and demonstrate an all-optical tomographic technique for measuring electronic spin states confined in quantum dots, that is both single shot, high fidelity, and can be performed on every polarization basis of our choosing. We employ this technique for thorough investigation of the depolarization of 5 different electronic spin qubits which are all confined in the same quantum dot device. We provide an experimental demonstration of a prototype device for deterministic generation of one-dimensional photonic cluster states. This device is based on a semiconductor quantum dot and utilizes the spin of the dark exciton as an entangler. Our prototype device can produce strings of a few hundred photons in which the entanglement persists over five sequentially emitted photons.