  We present a classical optics simulation of the one-dimensional Dirac
equation for a free particle. Positive and negative energy components are
represented by orthogonal polarizations of a free propagating beam, while the
spatial profile represents the spatial wave function of the particle. Using a
completely tunable time parameter, we observed the oscillation of the average
value of the Dirac position operator - known as zitterbewegung (ZB). We are
also able to measure the so called mean-position operator which is a
single-particle observable and presents no oscillations. Our work opens the way
for optical simulation of interesting phenomenon of relativistic systems, as
well as condensed-matter physics, without any requirement for specially
engineered medium.
