  We analyze work done on a quantum system driven by a control field. The
average work depends on the whole dynamics of the system, and is obtained as
the integral of the average power operator. As a specific example we focus on a
superconducting Cooper-pair box forming a two-level system. We obtain
expressions for the average work and work distribution in a closed system, and
discuss control field and environment contributions to the average work for an
open system.
