Condensed Matter Seminar Series

Title: Qubits from Superconducting Circuits

David P. DiVincenzo

IBM T. J. Watson Research Center

Thursday October 12,  11:30 am,  Room 298,  Physics Building

Abstract:  Many experiments over the last five years or so (at IBM and elsewhere) show that superconducting electric circuits containing Josephson junctions can behave like reasonably coherent quantum two-level systems.  We have a theoretical framework for explaining all these results; the Kirchhoff circuit laws can be viewed as the Hamilton equations of a classical mechanics.  This mechanics is of a massive particle in a multidimensional potential.  The most important features of this potential are determined by the placement of junctions in the circuit, but the ordinary inductances and capacitances of the circuit are key parameters as well for determining this potential.  The flexibility of electrical engineering provides a big design space for the construction of many different types of potentials with useful quantum behavior.  I will run through some examples of this analysis and how it has applied to several recent experiments.  There is also a circuit-level theory of decoherence in these systems.