Dear colleagues,

this Wednesday we have a colloquium about

Superconducting structures for quantum computing, 28. April 2004

Gianni Blatter Theoretical Physics, ETH Zuerich

"Quantum information holds the promise for novel cryptographic and computational schemes. Their implementation requires new types of `quantum' hardware which fulfills two conflicting requirements, controllability and simultaneous protection from the environment. The quantum optics-, solid state-, and NMR communities pursue major programs with the goal to achieve quantum control on manmade structures. The state of art involves assemblies of trapped ions performing specific tasks (controlled NOT gate, simple algorithms), a tailored molecule factorizing 15 via an NMR pulse sequence, the first measurement of an individual spin on a quantum dot, and controlled gate operations in superconducting structures. While these achievements look very promising, further advances in design and fabrication are needed in order to achieve the fault tolerance required for quantum computing. Here, we concentrate on superconducting devices and discuss novel design elements implemented in a charge- and flux-frustrated superconducting qubit with tetrahedral symmetry. Important new features are a relaxed fabricational constraint on the Josephson junctions and potentially long decoherence times due to a quadratic noise-susceptibility. Also, this device involves a simple idle state with a doubly degenerate ground state which does not suffer from strong decoherence via phonon radiation, one of the most dangerous sources of decoherence in superconducting quantum devices."

See also http://www.physik.unizh.ch/teaching/kolloquium.html for details.