In this Bachelor thesis we conducted extensive research on open optical micro cavities with different radii of curvature, analyzing their eigenmodes at varying cavity lengths. Our study focused on...Show moreIn this Bachelor thesis we conducted extensive research on open optical micro cavities with different radii of curvature, analyzing their eigenmodes at varying cavity lengths. Our study focused on three key aspects relevant to the characterization of these eigenmodes. First we analyzed the quality of relevant optical tools, namely a quarter waveplate and a polarization resolved CCD. We concluded that the quarter waveplate does not convert linearly polarized light into circularly polarized light and is therefore not reliable to use in measurements. The polarization resolved CCD was found to be very accurate in all four polarization channels. Second, we studied the fundamental mode. We measured that all fundamental modes were elliptical and the waists have a stronger polarization dependence than expected. We attribute this surprisingly strong effect to the angle and polarization dependent transmission of the Distributed Bragg Reflectors. Third, we studied the N=1 and N=2 modes by trying to find their modal amplitudes. Via this approach we were able to produce vector fields similar to the measured data, although the widths obtained for the fundamental mode did not align with those of the higher-order modes. Despite this mismatch we still believe modal analysis is a promising approach for analysing the eigenmodes of micro cavities.Show less
In this thesis, we work towards a demonstration of quantum key recycling (QKR) using photonic spatial modes. To that end, we first extend the security analysis of QKR provided in Fehr and Salvail’s...Show moreIn this thesis, we work towards a demonstration of quantum key recycling (QKR) using photonic spatial modes. To that end, we first extend the security analysis of QKR provided in Fehr and Salvail’s 2016 paper ’Quantum Authentication and Encryption with Key Recycling’ to accommodate for higher dimensional states and to allow for lossy environments. We then show how QKR can be realised using photonic spatial modes and we propose a setup that facilitates it up to a distance of 10 m with a 10% error probability as we confirm by simulation. Next, the theoretical predictions are tested using the classical analogue to single photons, the laser. We show that theory and experiment coincide to such a degree that theoretical expectations are experimentally viable. Finally, we discuss what modifications are required to genuinely demonstrate quantum key recycling using photonic spatial modes.Show less
Cluster states are a viable resource for quantum computing where information is stored in these states and one single-qubit measurement is performed at a time. In order to generate such states, we...Show moreCluster states are a viable resource for quantum computing where information is stored in these states and one single-qubit measurement is performed at a time. In order to generate such states, we use the quanta of light - photons - as our qubits. We generate them from a quantum dot in a microcavity which serves us as a deterministic single photon source. We explore a method of generating cluster states by entangling these photons with the means of linear optical elements and post-selection. We develop a theoretical model and show that it is in an agreement with our experimental data with single photons. From this agreement, we conclude that the cluster states arise in the experimental setup and the entanglement between the photons can be confirmed to be present with further analysis using our hypothesis and possibly even the quantum state tomography in the future.Show less
