  We study the fluctuations of the work performed on a driven quantum system,
defined as the difference between subsequent measurements of energy
eigenvalues. These work fluctuations are governed by statistical theorems with
similar expressions in classical and quantum physics. In this article we show
that we can distinguish quantum and classical work fluctuations, as the latter
can be described by a macrorealistic theory and hence obey Leggett-Garg
inequalities. We show that these inequalities are violated by quantum processes
in a driven two-level system and in a harmonic oscillator subject to a
squeezing transformation.
