An article about vanishing decoherence for certain parameters of an environment. In this paper, the authors study an environment that can undergo a quantum phase transition depending on the value of the coupling to the system (similar to Quan et al and Cucchietti et al ). The authors are surprised that the environment (an XY spin chain where gamma is the anisotropy parameter) does not produce decoherence for gamma=0. Actually, this is a trivial finding: for gamma=0 the model conserves the Z projection of the spin, so it commutes with the system-environment interaction and only the eigenenergies change. This is all because at gamma=0 the XY model belongs to a different class than for gamma .not.= 0 (the Ising universality class), and does not have a quantum phase transition as far as I know. 

The only thing I like about the paper is at the end there are some comments about starting with excited states (not the ground) which would be useful (if true) for some calculations I am doing.

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Posted by fercook to Science at 7/31/2006 01:48:42 PM

Labels: reviews, science