| Ultrabright Source of Polarization-Entangled Photons from Cavity-Enhanced Downconversion (2006) | |||||||||||
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| Ultrabright Source Polarization Entangled Photons from Cavity Enhanced Downconversion Christopher Edward Kuklewicz Submitted the Department Physics partial fulfillment the requirements for the degree Doctor Philosophy the MASSACHUSETTS INSTITUTE TECHNOLOGY October Christopher Edward Kuklewicz Author Department Physics October Certified Erich Ippen Professor Thesis Supervisor Certified Franco Wong Senior Research Scientist Thesis Supervisor Accepted Thomas Greytak Chairman Department Committee Graduate Students Ultrabright Source Polarization Entangled Photons from Cavity Enhanced Downconversion Christopher Edward Kuklewicz Submitted the Department Physics October partial fulfillment the requirements for the degree Doctor Philosophy Abstract This thesis describes the design construction and testing new source entanglement The goal produce pairs photons which are not only polarizationentangled but also have high brightness within narrow bandwidth This novel source more suitable than previous SPDC sources for transferring entanglement future qubit storage such trapped rubidium memory The narrow bandwidth imposed modifying the spectrum the photon pairs performing the downconversion inside cavity The collinear downconversion geometry inside the linear cavity achieved using quasi phased matched periodically poled potassium titanyl phosphate PPKTP crystal The single pass free space photon pairs produced were demonstrated polarization entangled measuring the Hong Mandel interference . This thesis describes the design, construction, and testing of a new source of entan- glement. The goal is to produce pairs of photons which are not only polarization- entangled, but also have a high brightness within a narrow bandwidth. This novel source is more suitable than previous SPDC sources for transferring entanglement to future qubit storage such as a trapped rubidium memory. The narrow bandwidth is imposed by modifying the spectrum of the photon pairs by performing the down- conversion inside a cavity. The collinear downconversion geometry inside the linear cavity is achieved by using a quasi-phased-matched periodically-poled potassium ti- tanyl phosphate (PPKTP) crystal. The single-pass free-space photon-pairs produced were demonstrated to be polarization-entangled by measuring the Hong-Ou-Mandel interference dip and measuring a violation of Bell’s inequality of 2.711±0.010 (which was greater than the classical limit of 2). The cavity-enhanced downconversion was observed with a brightness of 0.7 pairs/s per mW of pump per MHz of bandwidth in the Gaussian mode collected (a generation rate of 110 pairs/s/mW/MHz is inferred). The interference dip from the pairs was measured to have a visibility of 75% when near the ideal equal-FSR operating point, where the pairs are in the biphoton triplet state. When detuned to have unequal FSR the output pairs show the an interference dip behavior consisting of a combination of triplet and singlet states that depends on the time separation of the pair as it leaves the cavity. The observed results corroborate detailed predictions of a Gaussian-state model of cavity-enhanced downconversion. | |||||||||||
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