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Title: Photonic quantum information processing with the complex Hadamard operator
Author: Lopez , Enrique Martin
ISNI:       0000 0004 5915 3829
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2014
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The exploitation of quantum mechanics for new technologies promises a revolution in computing, simulations, communication and metrology. In particular, quantum computation and simulation harness properties peculiar to quantum systems to process information using algorithms that run exponentially faster than their classical counterparts. While the Fourier Transform (FT) is a cornerstone tool for signal processing in science, engineering, and computing, the quantum version of the Fourier transform (QFT) is a key component of many quantum algorithms. And just as the FT has a generalisation known as the complex Hadamard, so the QFT is a special case of the quantum complex Hadamard (QCH) operator. This thesis reports implementations of the QFT and QCH, with photons in linear optical circuits, as core components for quantum information processing, quantum computation, and quantum simulations. The iterative QFT is implemented in 8hor's quantum factoring algorithm to demonstrate how qubits can be recycled to provide a resource saving. This included the first demonstration of two in-series photonic controlled logic gates. The four dimensional QCH was constructed with an internal phase implemented as a tuneable Berry phase to control quantum interference between two photons. A generator for this QCH, described as a highly connected graph, was simulated as a Hamiltonian, with full time evolution implemented in a fully reconfigurable optical network. Quantum simulations for the evolution of phonons in a model chain of atoms were performed, where QFT operators prepare and measure in a basis corresponding to localised excitations. Quantised vibrational wave packets in molecules, described as phonons in the harmonic approximation, were simulated
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available