A high brightness source of entangled photons

Abstract: In the field of quantum optics and its wide variety of applications it is essential to have high brightness sources of entangled photons. In this Bachelor project, the aim has been to produce such a source based on recent experimental setups [1] [2] with a so-called Sagnac interferometer to generate polarization-entangled photons. The source built shows high quality entanglement. High visibility polarisation coincidence fringes (99.5% visibility) were observed. Moreover a Bell’s inequality [6] in a CHSH-form[36] was violated by more than 44 standard deviations. Also the wavelength tuning of the source with respect to temperature and pump wavelength was analysed, revealing shifts in the degeneracy temperature of 0.020 nm/K and a shift of the signal and idler wavelengths of 0.046 nm/K. This thesis begins with an introduction which reviews the fundamental ideas of entanglement and it’s role in quantum mechanics in section 1. This section is continued by a general discussion of photonic entanglement, different types of photonic entanglement and a short discussion of how to measure this entanglement is presented. This is followed by a review of different tecniques of generating entangled photons in sections 2 and 3. In section 4, the experimental process of assembling the Sagnac interferometer is presented. This is followed by a review of experimental results, which includes a characterisation of the source in relation to temperature and pump wavelength tunability in section 5. Then, in section 6, a presentation and an experimental test of Bell’s inequalities are presented. Thereafter, concluding remarks are made regarding the outcome of this project and the potential of further investigations utilizing the source in sections 7 and 8.