Entanglement detection schemes and coherent manipulation of spin in quantum dots

The work contained in this thesis deals with two closely related topics. Papers I-III deal with charge transport statistics in nanoscale devices to investigate the presence of entanglement in the constituent electrons. We identify the contributions of entangled electron pairs to the current cross-correlations as a signature of entanglement. Paper IV treats the electric control of a quantum dot based spin qubit via Electric Dipole Spin Resonance.

In Paper I, we present a spin entanglement detection model in a hybrid nanoscale device, with a general entangler connected to a set of quantum dots and anti-collinear ferromagnetic contacts. Our model allows us to study the implications of a non-ideal detector in an entanglement detection scheme.

In Paper II, we investigate a scheme for generating and detecting orbitally entangled states in a device consisting of six quantum dots. The underlying process which enables our proposed scheme is sufficiently fast, even for the rapidly decaying quantum coherence of orbital states defined in a solid.

In Paper III, we investigate a minimal entanglement detection scheme based on measurements of current cross correlations. We find a significant reduction in the number of measurements required for an entanglement test.

In Paper IV, we investigate the optimisation of electrically controlling an electron spin in a gate defined semiconductor quantum dot. Specifically, we study how the shape of the quantum dot together with the direction of an in-plane magnetic field affect the spin relaxation rate and frequency of the induced Rabi oscillations.