Physics and Astronomy

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This is the collection for the University of Waterloo's Department of Physics and Astronomy.

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Browsing Physics and Astronomy by Author "Branczyk, Agata"

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    Customized nonlinearity shaping in imperfect or variable waveguides
    (University of Waterloo, 2019-05-31) Kelly-Massicotte, Jérémy; Branczyk, Agata; Strickland, Donna
    Generation of high-quality single photons via heralded parametric downconversion re- quires careful design of spectral correlations in down-converted photon pairs. One step in this design process involves customized engineering of ferroelectric domains. In this thesis, we explore two aspects of such customized domain engineering. We first explore the impact of fabrication imperfections on two main domain engineering methods, by simulating domain variations in domain engineered structures. We quantify the impact by calculating the purity and amplitude of the generated photon. We conclude that realistic fabrication imperfections do not impair purity and amplitude significantly for the studied methods. However, high variations of the dispersion relations in the crystal impact purity and amplitude significantly. We then introduce two new domain engineering methods designed for mediums with varying dispersion relations. The first is a generalization of an existing algorithm used to design the domain configurations. The second method relies on varying the domain sizes. We show that the first method yields modest improvement, while the second one works remarkably well, even in conditions with extreme change in dispersion.
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    Optics, Loss and Gravity
    (University of Waterloo, 2021-01-13) Adjei, Eugene; Branczyk, Agata; Mosca, Michele
    We look at some ideas that can be found from making connections among optics, non-Hermitian dynamics and gravity. Using nonlinear optics, we demonstrate how loss can be used to make brighter sources of thermal light. Also, we simulate accelerating Unruh-DeWitt detectors in 1+1 spacetime using a nonlinear-optical setup engineered to have variable dispersion. In our last connection with gravity, we make a connection between a dynamic spacetime metric from linearized gravity and a spacetime-dependent refractive index from a linear-optical setup. From these connections with gravity, we argue that spacetime might be emergent, and that one should not quantize the metric to find a quantum gravity theory. Instead, we propose that gravity might have a gauge theory description and that the problem of quantizing gravity is equivalent to that of quantizing a gauge field. A gauge theory of gravity will make it possible to include this interaction into the Standard Model, and this inclusion may have implications for physics beyond the Standard Model.
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    Tuneable Hybrid and Multimode Squeezed States of Light
    (University of Waterloo, 2020-09-03) Drago, Christian; Branczyk, Agata
    Gaussian quantum states of light have many applications in quantum technologies. Two of the most widely used Gaussian quantum states of light are the single- and two-mode squeezed states. In this thesis, we propose the generation of a hybrid of these two states, which has both properties of single- and two-mode squeezed states. We then extend our method to the generation of multimode squeezed states which posses N-partite entanglement. Our states are defined using Gaussian frequency modes, and our method relies on a nonlinear-optical process called spontaneous parametric downconversion. We shape the joint spectral amplitude of the generated light in two ways, by spectrally engineering the light incident on the crystal and by the engineering of the nonlinear crystal to have desired properties. We first use our method to generate tuneable hybrid squeezed states and then extend it to multimode squeezed states. We then investigate design considerations for the nonlinear crystal and study the effect of fabrication errors. The tuneable hybrid and multimode squeezed states are localized in both frequency and time, making them ideal for a variety of quantum information protocols. We expect that the states will be used to generalize many quantum information protocols to their multimode counterparts, such as, multi-parameter quantum metrology, multi-channel quantum imaging and multi-partite teleportation. Our work will therefore broaden the applicability of optics for the development of quantum technologies.