Master defence by Kasper Ejdal Lund

Quantum Gates in Photonic Waveguides

Abstract:

Self-assembled quantum dots embedded in photonic crystals provide a platform on which it is possible to tailor the light-matter interaction in great detail. This makes these systems promising candidates for the implementation of quantum communication networks, due to the ability of interfacing stationary quantum dos with propagating photons.

This talk provides a proposal to implement a controlled phase gate by using a strong in- teraction between three self-assembled quantum dots. Two of these dots are used to implement the qubit, while the third auxiliary emitter is used to herald the gate. It is possible to control the dynamical change of phase of the qubits by illuminating the auxiliary quantum dot with a weak laser field. This will project the auxiliary quantum dot into a definite state, due to the nature of the dynamics. The primary source of error will project the auxiliary into another state; it is thus possible to check whether the gate has succeeded or not by measuring the state of the auxiliary emitter, giving the gate an integrated error detection.

This talk will report on a method to obtain a unity fidelity for this controlled phase gate and will report on the behaviour of the success probability. In addition, errors induced by variations in the physical parameters of the quantum dots are discussed and methods of mitigating these errors are presented.