  We discuss the random motion of charged test particles driven by quantum
electromagnetic fluctuations at finite temperature in both the unbounded flat
space and flat spacetime with a reflecting boundary and calculate the mean
squared fluctuations in the velocity and position of the test particle. We show
that typically the random motion driven by the quantum fluctuations is one
order of magnitude less significant than that driven by thermal noise in the
unbounded flat space. However, in the flat space with a reflecting plane
boundary, the random motion of quantum origin can become much more significant
than that of thermal origin at very low temperature.
