  In this brief note I try to give a simple example of where physical intuition
about a collection of interacting qubits can lead to the construction of
"natural" versions of what are, generically, quite abstract mathematical
objects - in this case graph invariants.
  This note is written primarily for physicists who do not want to go through
the painful process of trying to understand Ed Witten's vastly more complicated
construction of physically intuitive knot invariants, but who'd like some idea
of how physical intuition can play a role in such things.
