PHOTONIC ENTANGLEMENT IN QUANTUM COMMUNICATION AND QUANTUM COMPUTATION

Since ISQM 05, entangled photons have been used in our laboratory for a number of novel experiments, both in the foundations of quantum mechanics and in quantum information. Because of the high quality of entanglement of photons, precision tests of a non-local realistic theory proposed by Leggett were possible. These experiments indicate that the concept to be abandoned in quantum mechanics is most likely that of objectivism or realism. In parallel experiments, many schemes of one-way quantum computation were performed. There, because of active feed-forward, one can realize an efficient quantum computer and eliminate the effect of the randomness of individual events. The most significant properties of all-optical quantum computation are the very short cycle time, which can easily be below 100 ns and the high fidelity of the operation. Finally, experiments on quantum entanglement over distances of up to 144 km not only confirmed that quantum communication with satellites is possible, they also allowed novel tests of Bell's inequality.