  The Heisenberg picture and Schrodinger picture are supposed to be equivalent
representations of quantum mechanics. However this idea has been challenged by
P.A.M. Dirac. Also, it has been recently shown by A. J. Faria et al that this
is not necessarily the case. In this article a simple problem will be worked
out in quantum field theory in which the Heisenberg picture and Schrodinger
picture give different results.
