This thesis is based upon the work I have done during my PhD candidature at
Macquarie University. In this work we develop quantum technologies that are
directed towards realising a quantum computer. Specifically, we have made many
theoretical advancements in a type of quantum information processing protocol
called BosonSampling. This device efficiently simulates the interaction of
quantum particles called bosons, which no classical computer can efficiently
simulate. In this thesis we explore quantum random walks, which are the basis
of how the bosons in BosonSampling interfere with each other. We explore
implementing BosonSampling using the most readily available photon source
technology. We invented a completely new architecture which can implement
BosonSampling in time rather than space and has since been used to make the
worlds largest BosonSampling experiment ever performed. We look at variations
to the traditional BosonSampling architecture by considering other quantum
states of light. We show a worlds first application inspired by BosonSampling
in quantum metrology where measurements may be made more accurately than with
any classical method. Lastly, dealing with BosonSampling, we look at
reformulating the formalism of BosonSampling using a quantum optics approach.
In addition, but not related to BosonSampling, we show a protocol for
efficiently generating large-photon Fock states, which are a type of quantum
state of light, that are useful for quantum computation. Also, we show a method
for generating a specific quantum state of light that is useful for quantum
error correction --- an essential component of realising a quantum computer ---
by coupling together light and atoms.Comment: PhD Thesi