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On Integrated Photonic Quantum Simulations On Integrated Photonic Quantum Simulations Devon N. Biggerstaff B.Sc., The University of Puget Sound M.Sc., The University of Waterloo A thesis submitted for the degree of Doctor of Philosophy at The University of Queensland in 2014 School of Mathematics and Physics i Abstract Quantum information science has the potential to greatly enhance our capabilities for secure communication through quantum encryption and communication technologies; for measure- ment sensitivity through quantum metrology; and for certain computational tasks through quantum computers. In particular, simulations of complex quantum systems|using either quantum computers or other, better-controllable quantum systems|have the potential to greatly improve our understanding of the states and dynamics of processes such as the fold- ing of proteins, dynamics in chemistry, and energy transport on molecular and cellular scales. This thesis concerns experimental quantum information science, in particular quantum simu- lations, conducted using classical and quantum states of light in arrays of coupled laser-written waveguides. Integrated quantum photonics, wherein optical quantum states are manipulated in waveguide arrays, will be crucial for the miniaturization and ultimate practical scalability of optical quantum simulation and computing. Such waveguide arrays are also particularly well-suited for some quantum simulations due to the similarity between the scalar, paraxial optical wave equation and Schrodinger's equation for a bound quantum particle. Four experiments are described in this thesis where laser-written waveguide arrays are employed for optical quantum information science. Two of these concern waveguide optical simulations inspired by exciton transport dynamics in photosynthetic structures. For the first of these, we detail the design, modeling, and testing of a waveguide array for analog simulation of the Hamiltonian governing exciton dynamics in a particular bacterial photosynthetic sub- unit. We ultimately find that such a demanding simulation may exceed current capabilities in the rapidly-maturing field of laser-written waveguides, but the modeling and measurement techniques developed inform our further experiments. In the other such experiment we study an important quantum transport phenomenon, environmentally-assisted quantum transport (ENAQT), which is hypothesized to partially explain high energy transport in photosyn- thetic light-harvesting. We show that the transport efficiency of light in a specific disordered waveguide array can be enhanced through the addition of quantum decoherence which we implement by broadening the illumination bandwidth. Another experiment concerns the behavior of two-photon states in a continuous-time quan- ii tum walk with periodic boundary conditions implemented in an elliptic waveguide array. We use results from classical-light characterization to predict the outcomes of measurements of two-photon correlations in the array. The final experiment in this thesis details the design, modeling, fabrication, and testing of laser-written unitary circuits for heralded two-photon entangling quantum gates. We study the action of such devices in the presence of fabrication imperfections, characterize our circuits using classical and quantum interference techniques, and show such circuits to be good candidates for heralded photonic gate fabrication. iii Declaration by author This thesis is composed of my original work, and contains no material previously published or written by another person except where due reference has been made in the text. I have clearly stated the contribution by others to jointly-authored works that I have included in my thesis. I have clearly stated the contribution of others to my thesis as a whole, including statistical assistance, survey design, data analysis, significant technical procedures, professional editorial advice, and any other original research work used or reported in my thesis. The content of my thesis is the result of work I have carried out since the commencement of my research higher degree candidature and does not include a substantial part of work that has been submitted to qualify for the award of any other degree or diploma in any university or other tertiary institution. I have clearly stated which parts of my thesis, if any, have been submitted to qualify for another award. I acknowledge that an electronic copy of my thesis must be lodged with the University Li- brary and, subject to the General Award Rules of The University of Queensland, immediately made available for research and study in accordance with the Copyright Act 1968. I acknowledge that copyright of all material contained in my thesis resides with the copy- right holder(s) of that material. Where appropriate I have obtained copyright permission from the copyright holder to reproduce material in this thesis. iv Publications during candidature 1. James. O. Owens, Matthew. A. Broome, Devon. N. Biggerstaff, Michael. E. Gog- gin, Alessandro Fedrizzi, Trond Linjordet, Martin. Ams, Graham. D. Marshall, Ja- son. Twamley, Michael. J. Withford, and Andrew. G. White. Two-photon quantum walks in an elliptical direct-write waveguide array. New Journal of Physics 13, 075003 (2011). 2. Martin Ringbauer, Devon N. Biggerstaff, Matthew A. Broome, Alessandro Fedrizzi, Cyril Branciard, and Andrew G. White. Experimental joint quantum measurements with minimum uncertainty. Physical Review Letters 112, 020401 (2014). 3. Thomas. Meanyy, Devon. N. Biggerstaff y, Matthew. A. Broome, Alessandro. Fedrizzi, Michael. Delanty, Michael. J. Steel, Alexei. Gilchrist, Graham. D. Marshall, Andrew. G. White, and Michael. J. Withford. Engineering integrated photonics for heralded quantum gates. Submitted to Light: Science and Applications (August 2014). 4. Devon N. Biggerstaff, Ren´eHeilmann, Aidan A. Zecevik, Markus Gr¨afe,Matthew. A. Broome, Alessandro. Fedrizzi, Stefan Nolte, Andrew. G. White, and Ivan Kassal. Enhancing quantum transport in a photonic network using controllable decoherence. Submitted to Nature Photonics (November 2014). yCo-equal first authors. v Publications included in this thesis J. O. Owens, M. A. Broome, D. N. Biggerstaff, M. E. Goggin, A. Fedrizzi, T. Linjordet, M. Ams, G. D. Marshall, J. Twamley, M. J. Withford, and A. G. White. Two-photon quantum walks in an elliptical direct-write waveguide array. New Journal of Physics 13, 075003 (2011). Incorporated as Ch.6. Contributor Statement of contribution D. N. Biggerstaff Primarily responsible for circuit modeling (50%). Contributed signifi- cantly to the first (25%) and final (25%) manuscript drafts. J. O. Owens Shared primary responsibility for experiment design (40%) and con- struction (40%), data acquisition (50%), and data analysis (40%). Con- tributed significantly to circuit modeling (25%) and preparation of the first draft of the manuscript (20%). Contributed to final manuscript draft (10%). M. A. Broome Shared primary responsibility for experiment design (40%) and con- struction (40%), data acquisition (50%), and data analysis (40%). Con- tributed significantly to circuit modeling (25%), preparation of the first draft of the manuscript (30%), and the final manuscript draft (25%). Coordinated publication process and authored referee replies (100%). M. E. Goggin Contributed significantly to the experiment construction (20%). Con- tributed to the final manuscript draft (10%). A. Fedrizzi Contributed supervision to the experiment design (20%) and construc- tion and data analysis. Contributed significantly to the first (25%) and final (25%) manuscript drafts. T. Lindjordet Primarily responsible for optical circuit design and fabrication (60%). M. Ams Supervised and contributed to optical circuit design and fabrication (10%). G. D. Marshall Supervised and contributed to optical circuit design and fabrication (10%). J. Twamley Supervised and contributed to optical circuit design and fabrication (10%). M. J. Withford Supervised and contributed to optical circuit design and fabrication (10%). A. G. White Contributed to supervision of experiment construction, data analysis, and the first manuscript draft. Contributed to the final manuscript draft (5%). vi D. N. Biggerstaff, T. Meany, M. A. Broome, A. Fedrizzi, M. Delanty, M. J. Steel, A. Gilchrist, G. D. Marshall, A. G. White, and M. J. Withford. Engineering integrated photonics for heralded quantum gates. Submitted to Light: Science and Applications (August 2014). Incorporated as Ch.8. Contributor Statement of contribution D. N. Biggerstaff Primarily responsible for design and construction of circuit testing ap- paratus (70%) and data acquisition (90%). Fully responsible for data analysis (100%). Contributed significantly to new theory and circuit modeling (40%). Primarily responsible for first (60%) and final (75%) manuscript drafts. Coordinated manuscript submission process (100%). T. Meany Contributed to initial concepting (10%). Primarily responsible for op- tical circuit design (60%) and fabrication (80%). Contributed to design and construction of circuit testing apparatus (10%). Contributed signif- icantly to the first manuscript draft (25%). M. A. Broome Contributed significantly to design and construction of circuit testing apparatus (20%). Contributed to data acquisition (10%). A. Fedrizzi Contributed to initial concepting (10%). Contributed supervision to the experiment design and construction and data analysis. Contributed to the first (5%) and final (5%) manuscript drafts. M. Delanty Contributed to initial concepting (5%) and circuit design (10%). M.
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