Abstract (eng)
Quantum mechanics was initially developed to describe microscopic processes but scientists quickly came to far-reaching predictions, such as the wave-particle dualism of matter [1,2] or the entanglement of particles [3,4], which often contradict our classical intuition. However, not even a single experiment could falsify any theoretical prediction of quantum mechanics. Today it is the most tested theory in physics. The question of the range and limits of its validity arises. To which extend can systems be macroscopic, complex and massive while retaining their quantum features? Is there a spatial and temporal restriction to the separation of wave functions? Which decoherence mechanisms force systems at macroscopic scales to appear classical?
During my thesis I focused theoretically as well as experimentally on matter-wave interferometry with atoms, molecules and molecular clusters.
During my 3 month exchange stay in the group of Prof. Müller at the University of California at Berkeley we have carried out an experiment to show the largest space-time area interferometer at that time [5]. Here, matter waves of caesium atoms have been coherently split and recombined up to 8.8 mm and for 500 ms. Key to run this experiment was to compensate for earth´s rotation. Without this compensation the Coriolis force would have prevented the split matter-waves from a precise recombination.
The main subject of my thesis at the University of Vienna was the experimental realization of the (first) all Optical Time-domain Ionizing Matter-wave (OTIMA) interferometer [6,7]. It consists of three pulsed nanosecond standing light waves which act on the particles with a well-defined timing sequence. Interference in the time-domain is independent of the particles’ velocities and of their de Broglie wavelengths. This has been demonstrated earlier for atoms by addressing laser light to certain atomic levels [8]. In contrast to that, the OTIMA interferometer uses optical ionization gratings [9] which allow us to coherently manipulate many atoms, molecules and nanoparticles, since photo ionization is mostly independent of the specific internal level structure of the nanoparticle. As a result we can interfere different particles simultaneously. Quantum interference in the OTIMA setup is not only visible in the spatial interference pattern but also in the mass selective transmission, which is a feature of the time-domain. This has been proven for Anthracene clusters up to 2300 amu [6]. The interference pattern has a period of 78.5 nm and is therefore highly sensitive to external forces. This feature as well as the accurate timing of the OTIMA offer an enormous advantage for future deflectometry experiments.
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