Atomic Physics, Quantum Optics, Miniaturizing on a chip

The development of microelectronics and information technology in the second half of the 20th century has shown that findings from fundamental science can generate robust applications by means of miniaturisation and integration. The aim of Jörg Schmiedmayer`s AtomChip project is to attain that very objective in quantum optics and quantum physics with atoms and photons. The purpose of these research efforts is to investigate the fundamental physics of miniaturisation and integration. On the AtomChip, atoms are captured, quantum- manipulated and detected using nanostructured atom traps and microoptics. The goal is to develop a quantum toolbox which allows experimentation in a wide variety of quantum worlds and to build quantum bridges between those worlds. The applications range from ultra-precise sensors to quantum information processing.

Miniaturization and integration are important steps towards a robust application of fundamental physics. Successful examples are semiconductor physics and its application in the integrated circuits of information processing and the development of integrated microoptics and their applications in sensor and communication technology. One of the central objectives of this Wittgenstein project was to lay the foundations for a similar development in quantum physics, and thus point the way to the development of a robust quantum technology by means of miniaturization and integration. We followed two different paths: (1) Integrated experiments with ultra - cold quantum gases on AtomChips; (2) the quantum interconnect project (QuIC) where we investigated the quantum connection between different systems to build hybrid quantum systems. AtomChips combine the best of both worlds: Cold atoms a system, which is very suitable for accurate quantum manipulation - and the technological possibilities of nanofabrication. This enabled us to build robust experiments for studies of complex quantum systems. A central question was: Does a completely isolated many-body quantum system relax to an equilibrium, as we know from statistical mechanics? Employing interference experiments with one-dimensional Bose-Einstein-Condensates we could show that properties of classical physics in such an isolated quantum systems arise autonomous, that this de-coherence emerges locally, and finally spreads in a causal light cone like fashion throughout the entire system. This indicates a close link between microscopic quantum physics and macroscopic (classical) statistical physics. In the quantum Interconnect Project, we investigated quantum connections between photons, spins and superconducting circuits. We established and studied the coupling of superconducting circuits to electron and nuclear spin ensembles, which are promising candidates for a quantum memory. We built a new experiment to ultra - cold atoms to couple and investigate superconducting. We developed new protocols for quantum information processing based on photonic modules coupling photons and NV centres in diamond. The photons transmit qubits between the nodes, the NV centres are small 2-qubit processors with a long lived quantum memory. We could show that this new protocol allows fault-tolerant quantum of information processing with existing technology. In the Lab we took the first steps towards implementation of such photonic modules by miniaturized and integrated structures on a chip.