  The dynamical behavior of a quantum many-particle system is characterized by
the lifetime of its excitations. When the system is perturbed, observables of
any non-conserved quantity decay exponentially, but those of a conserved
quantity relax to equilibrium with a power law. Such processes are associated
with a dynamical exponent $z$ that relates the spread of correlations in space
and time. We present numerical results for the Fredkin model, a quantum spin
chain with a three-body interaction term, which exhibits an unusually large
dynamical exponent. We discuss our efforts to produce a reliable estimate
$z$=3.16(1) through direct simulation of the quantum evolution and to explain
the slow dynamics in terms of an excited bond that executes a constrained
random walk in Monte Carlo time.

Strongly Correlated Electrons