  The effect of quenched disorder in a many-body system is experimentally
investigated in a controlled fashion. It is done by measuring the phase
synchronization (i.e. mutual coherence) of 400 coupled lasers as a function of
tunable disorder and coupling strengths. The results reveal that correlated
disorder has a non-trivial effect on the decrease of phase synchronization,
which depends on the ratio of the disorder correlation length over the average
number of synchronized lasers. The experimental results are supported by
numerical simulations and analytic derivations.
