Friday, July 8, 2011

Quantifying vibronic entanglement

I just finished a paper, Quantum entanglement between electrons and vibrations in molecules, with Laura McKemmish, Noel Hush, and Jeff Reimers.
We consider a simple model Hamiltonian which describes two quantum states interacting with a single vibrational mode [alternatively known as the one mode spin-boson model, the Herzberg-Teller model, or the E x beta Jahn-Teller model].

A couple of things I learnt:
*Realistic model parameter values for six molecules including ammonia, benzene, and semibulvalene.
*The large entanglement which occurs in the strong coupling (adiabatic) limit can be quite "fragile". i.e., it can be destroyed by  a small asymmetry in energy. Compare the top left two boxes in the figure below which shows a colour-shaded plot of the entanglement as a function of the Hamiltonian parameters.
*In contrast, in a regime where all the energy scales are comparable, the entanglement is much more robust.
A curious side anecdote about this paper. Last week we first sent the paper to Physical Review A. However, an editor did not consider it would be "of interest to their readers" and so would not send it out for review. I found that rather disappointing. I wondered if that was because there was a passing reference to Penrose and Hameroff in the conclusion. So, we removed that reference and sent the paper to Journal of Chemical Physics. I would be curious to hear from "Phys. Rev. A readers" whether they think the paper is of interest.

1 comment:

  1. I am an occasional reader of Phys. Rev. A, and this paper is definitely of interest to me.