Condensed Matter Physics Seminar

Thursday, March 9, 2000, 2 p.m.
Plant Sciences Building, Room 1130

Mechanisms of Decoherence

Philip Stamp

(Spinoza Institute, University of Utrecht, Netherlands)

Abstract:  A large worldwide effort is underway to make quantum devices which use quantum coherence and interference properties to their fullest extent.  This research includes proposals to make a "quantum computer" by linking together mesoscopic or nanoscopic "qubits"; such a computer is supposed to have exponentially greater computing power than a classical computer.

However condensed matter physicists involved in such work must deal with the fundamental problem of decoherence. The question of what mechanisms control decoherence (the loss of phase coherence in a quantum system) is of central interest in fields ranging from cosmology to mesoscopics and quantum optics.  Amongst other things one would like to know if decoherence can be reduced to arbitrarily small levels, or whether it saturates at some minimum value.  In this talk I will discuss recent work (both experimental and theoretical) in magnetic and superconducting systems, which indicates that there may only be two kinds of decoherence in Nature.  It also shows that there are mechanisms of decoherence which persist down to zero temperature.  I will discuss the implications of these results for quantum device design, as well as for more general questions about the crossover between quantum and classical physics.

Host: Victor Yakovenko

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