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SYDP: Dissertation Prize Symposium

SYDP 1: AMOP Dissertation Prize Symposium

SYDP 1.1: Hauptvortrag

Montag, 8. März 2010, 16:30–17:00, F 107

Experimental all-optical one-way quantum computing — •Robert Prevedel — Faculty of Physics, University of Vienna, Austria

In recent years, one-way quantum computing has become an exciting alternative to existing proposals for quantum computers. In this specific model, coherent quantum information processing is accomplished via a sequence of single-qubit measurements applied to an entangled resource known as cluster state. In our experiments, we generate a photonic four-qubit cluster state by means of parametric down-conversion. In one-way quantum computation, the random quantum measurement error can be overcome by applying a feed-forward technique, such that the future measurement basis depends on earlier measurement results. This technique is crucial for achieving deterministic quantum computation once a cluster state is prepared. Using custom-built, ultra-fast electro-optical modulators, we show the first experimental realization of fast, active feed-forward, achieving gate times of less than 150ns. This allowed experimental demonstrations of various quantum algorithms, consisting of a few gates. Among them the so-called Deutsch-Josza algorithm, an important quantum algorithm that is capable of distinguishing whether a function is constant or balanced and the implementation of a quantum game known as Prisoner's Dilemma. Furthermore we were able to design decoherence-free subspaces for cluster states which achieve remarkable protection from environmentally induced decoherence, delivering nearly ideal computational outcomes.