Degree Year


Document Type


Degree Name

Bachelor of Arts


Physics and Astronomy


Stephen FitzGerald


Bell, Entangle, Entangled, Entanglement, Optics, Experiment, Inequality, Downconversion, Nonlinear, Photodiode, Polarization, Coincidence, Violation, Quantum cryptography


The thesis documents the work done over the year to initiate an undergraduate Advanced Laboratory experiment which tests Bell’s inequality. It provides reference theory for the experiment, including explanations of Bell inequalities, basics of nonlinear optics, type-I downconversion and entanglement, and polarization states of the entangled photons. A main result is the equipment and design proposal for the experiment, which will cost a total $19600, led in price by the $9000 of a four photodetector array and followed by the $5000 of a 405nm pump laser. Entangled photons are produced by pumping BBO in a two-crystal geometry. Although most of the light is transmitted, some undergoes type-I parametric downconversion. Degenerate pairs are in a tunable entangled state and can be used to show non-classical behavior. Specifically, a violation of the CHSH Bell inequality can be observed. Usable coincidence rates of several thousand per second are expected. Experimental and data analysis methods are described as the basis of future laboratory documentation. Explanations of equipment alignment and adjustment and data collection are included, as well as derivations of relevant analyses of the experimental data. Lastly the coincidence circuit built for the experiment is reviewed. The circuit costs less than $40 to construct and demonstrates a coincidence window of between 18ns and 36ns.

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