A classical interpretation of observed macroscopic quantum behavior in microwave driven Josephson systems


Date Thursday October 18th 2007
Time 4:00-5:00pm
Venue George E. Pake Auditorium

PARC Forum

We present a classical analysis of the Josephson response to externally applied microwave fields. We are especially interested in the Josephson behavior of zero-voltage states, since these have been intensely investigated experimentally due to signatures of macroscopic quantum behavior that may have applications in quantum information processing technology. The analysis of the standard classical model of Josephson circuits shows that many of the experimentally observed features can be found in the purely classical Josephson system if it is perturbed with pulsed microwave signals and subject to experimentally accurate thermal noise.

The classical features of interest arise from the dynamical response and transients to phase-locking of the oscillator to the external microwave signal. We exemplify the classical picture by making comparisons between the classical analysis and a few experimental observations of multi-peak switching distributions, Rabi-type oscillations, Ramsey-type fringes, and spin-echo type response as derived from the statistical microwave-induced escape from the potential well in a Josephson system.


Niels Gronbech Jensen is Professor in the Department of Applied Science at the University of California, Davis, and Faculty Scientist at the National Energy Research Scientific Computing Center (NERSC) of the Lawrence Berkeley National Laboratory. His research interests are in the area of atomic scale materials modeling and particle representation of matter such as vortex systems, soft matter, and granular materials. He also has an ongoing interest in the dynamics and phase locking of nonlinear oscillators and soliton systems.

Niels graduated in Physics from the Technical University of Denmark. Prior to joining UC Davis he held a postdoc position at Stanford University and a postdoc and staff position at Los Alamos National Laboratory.

He is the recipient of several awards, including the 1999 "R&D 100 Award" and the 1997 Los Alamos Award for "Excellence in Technology Transfer".

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