Karakterisering av en programmerbar fotonisk krets för enkel-foton-drift

Programmable integrated photonic circuits offer a compact, low-power and ver-satile method for the control of light. Unlike conventional electronics, photonictechnologies can operate at higher speeds and have increased bandwidth as mul-tiple wavelengths of light can be sent through a single optical fiber allowing forunparalleled transfer of information. By combining these impressive attributeswith single photons, the advantages of such circuits can be greatly enhancedas this allows for the possibility of secure quantum communication and thepossibility to use these circuits as a testbed for fundamental quantum physicsexperiments.The photonic circuit investigated in this thesis was a universal multiport inter-ferometer consisting of eight modes was calibrated for use in single photon exper-iments. This circuit used the rectangular architecture developed by Clementswhich consists of a mesh of MZIs and phase shifters in a silicon-on-insulatorplatform. The structure was designed using Nazca, with the waveguides andMMI couplers fabricated by SiPhotonIC technologies and the photonic packag-ing completed by Quix.Entangled photon pairs at 1550 nm generated by a Type- II periodically poledpotassium potassium titanyl phosphate crystal were used as the single photonsource in an experiment to emulate coherent perfect absorption. Given thatthe primary attraction of such an interferometer is the implementation of anyunitary operator, demonstrating an emulation of coherent absorption allows forthe possibility of implementing non-unitary matrices on such an interferome-ter through ancilla modes. The experiment modelled this absorption throughcoherent loss to an ancilla mode, tuning the absorption value by utilising thephase shifters to re-route the light while the input phase of the circuit was beingswept.This thesis opens up the door to further experiments involving loss and gainusing single photons by being able to tune their quantum interference. Modellingquantum phenomena has been a challenge for classical computers since theadvent of quantum mechanics due to the inherent differences between classicaland quantum computing and the inability to be able to accurately represent thequirks of quantum physics such as entanglement and superposition Thus, thedevelopment of these integrated quantum photonic circuits can directly lead tothe development of sophisticated, programmable quantum gates as well as theeventual execution of quantum information processing and simulation protocols.