Dicke Quantum Phase Transition In An Optical Cavity QED System

"Dicke Quantum Phase Transition in An Optical Cavity QED System"

Scott Parkins

University of Waikato, New Zealand

Wednesday, April 19, 2006 11 AM -12 Noon in 375 LeConte Hall

Abstract

The Dicke Model of an ensemble of two-state atoms interacting collectively
with single quantized mode of the electromagnetic field (without the
standard rotating-wave approximation) exhibits a zero-temperature quantum
phase transition to a super-radiant state at a critical atom-cavity coupling
strength; characteristically order parameters are the mean photon number and
atomic inversion. Here I describe a proposal based on multilevel atoms and
cavity-mediated Raman transitions to realize an effective Dicke system
operating in the phase transition regime. Cavity flourescence provides a

 measurable output channel from the system and it's properties display a 

variety of signatures of critical behavior in the transitional regime. The
scheme appears feasible with existing experimental parameters in both the
few-atoms and many-atom limits and offers possibilities for investigations of
entanglement in a quantum critical system. Variations of the scheme also enable

 one to engineer a variety of effective interacting-spin systems which also

exhibit quantum phase transitions and critical behavior of entanglement.