Optical Quantum Information with Non-Gaussian States

Lund, Austin (2008). Optical Quantum Information with Non-Gaussian States PhD Thesis, School of Physical Sciences, The University of Queensland.

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Author Lund, Austin
Thesis Title Optical Quantum Information with Non-Gaussian States
School, Centre or Institute School of Physical Sciences
Institution The University of Queensland
Publication date 2008-06
Thesis type PhD Thesis
Supervisor Prof. Timothy Ralph
Total pages 149
Subjects 240000 Physical Sciences
Formatted abstract
Quantum information and quantum computing offer a new range of possibilities in terms of
new computing algorithms, the ability to perform new types of operations and make statements
about information in terms of what it is physically possible to know about a system.
Experiments in quantum information and quantum computing have been advancing significantly,
especially over the last decade. In optical quantum computing there are two main
types of experiments that are performed today. They are experiments involving single photons
with information encoded on the polarisation of the photon and experiments involving
states with Gaussian noise profiles in their quadratures. There appears to be no way to
perform the required operations for universal quantum computing using operations which
take Gaussian states to Gaussian states. Universal quantum computing using single photons
is possible but uses either enormously large non-linearities or a large number of resources.
Also, operations which take Gaussian states to non-Gaussian states are not well understood
in general and can often be very difficult to implement.
This thesis presents three sources of optical non-Gaussian states which demonstrate some
of the interesting properties of these states. First, a scheme for universal quantum computing
using superpositions of coherent states is presented. Error correction and the fault tolerance
properties of this scheme is also explored and compared with current single photon architectures.
These gates require superpositions of coherent states as resources and a relatively
simple scheme is shown for how these states may be generated. Next a scheme for distilling
near ideal Gaussian entanglement using non-Gaussian operations is presented. The loss and
noise conditions under which ideal distillation can be achieved are presented. Finally, a verysimple way of generating mixed non-Gaussian states from two Gaussian states is presented.
These states are shown to give rise to counter-intuitive results when measuring their entanglement
and when analysing their operational ability in terms of teleportation and quantum
key distribution.
Keyword quantum optics, quantum computing, coherent state, entanglement distillation, entanglement purification

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Created: Tue, 02 Dec 2008, 14:52:34 EST by Mr Austin Lund on behalf of Library - Information Access Service