For a phenomenological explanation of the absence of macroscopic superpositions, mass-dependent nonlinear and stochastic terms are added to the Schrödinger equation in some models of wave function...Show moreFor a phenomenological explanation of the absence of macroscopic superpositions, mass-dependent nonlinear and stochastic terms are added to the Schrödinger equation in some models of wave function collapse. This thesis describes a feasibility study of a microwave interferometer experiment with the purpose of falsifying the existence of spontaneous wave function collapse. Traveling wave parametric amplifiers in the interferometer arms effectively increase the mass of these superpositions, resulting in an interference visibility and an expected vanishing visibility in case of wave function collapse. The main question arises if the visibilities for these cases can be distinguished from each other in case of a gain of 20 dB and a (typical) insertion loss of 4 dB of the parametric amplifiers. Calculations of the interference visibilities were extended and performed by a Python program with the QuTiP module by using a Master Equation solver and Monte Carlo simulations on different computer infrastructures with up to 1.5 TB of RAM available. The limitations of the solvers were the QuTiP internals and computational time respectively. Visibilities are calculated using the Master Equation solver for gains up to 13.4 dB when neglecting losses, and for gains up to 5.3 dB and insertion losses up to 6.5 dB when including the effect of dissipation using both solvers. The differences between both visibilities appear to converge to constant values in the limit of large gain. Further calculations can be carried out on the Lisa Cluster to explore this promising observation. In addition, a cryogenic calorimeter for determining the insertion loss of an amplifier is characterized by its thermal time constants. Efforts were made to reduce the time constant attributed to a 3 dB attenuator, allowing for a precise determination of its power dissipation. On the basis of the results of this study, it can be concluded that significant steps in determining the feasibility of the proposed interferometer experiment are taken and future research is encouraged.Show less
We have extended measures of bipartite entanglement to measures of multipartite entanglement for pure states. To better grasp the different ways in which a multipartite state may be entangled, we...Show moreWe have extended measures of bipartite entanglement to measures of multipartite entanglement for pure states. To better grasp the different ways in which a multipartite state may be entangled, we first give a more general definition of entanglement that is based on partitions of the particles. Then we present a measure corresponding to this definition and use both analytic and computational methods to gain insight in the manner in which the Wn and GHZn states are entangled. Although the overall entanglement of two general multipartite states is not straightforwardly comparable we conclude that the Wn states are less entangled than GHZn states for every partition of the particles.Show less
