  We consider the dynamics of charge carriers in single-layer graphene that are
subject to random temporal fluctuations of their mass gap. The optical
conductivity is calculated by incorporating the quantum-stochastic time
evolution into the standard linear-response (Kubo) theory. We find that, for an
intermediate range of frequencies below the average gap size, electron
transport is enhanced by fluctuations. At the same time, in the limit of high
as well as low frequencies, the conductivity is suppressed as the variance of
gap fluctuations increases. In particular, the dc conductivity is always
suppressed by a random temporal mass with nonvanishing mean value and vanishes
in the zero-temperature limit. Our results are complementary to those obtained
recently for static random-gap disorder in finite-size systems.
