Prof. Mark Dykman
Michigan State University

Date: Nov. 23, 2008

Title: Quantum activation and quantum measurements

Abstract:

Do systems far from thermal equilibrium have features that have no
analogue in equilibrium systems? Are there generic features that would
be model-independent? We address these questions by studying
metastable decay. The familiar decay mechanisms are tunneling and
thermal activation. We show that periodically modulated systems may
display a different decay mechanism, which we call quantum activation.
Here, decay occurs via quantum fluctuations induced diffusion over a
quasi-energy barrier. The decay rate displays scaling behavior near
critical parameter values where metastable vibrational states
disappear. We also show that the tunnel splitting of symmetric and
antisymmetric vibrational states oscillates and changes sign with
varying parameters. The results impose limitations on the
characteristics of bifurcation amplifiers used in quantum
measurements.