  Atoms falling into a black hole (BH) through a cavity are shown to enable
coherent amplification of light quanta powered by the BH gravitational vacuum
energy. This process can harness the BH energy towards useful purposes, such as
propelling a spaceship trapped by the BH. The process can occur via transient
amplification of a signal field by falling atoms that are partly excited by
Hawking radiation reflected by an orbiting mirror. In the steady-state regime
of thermally equilibrated atoms that weakly couple to the field, this amplifier
constitutes a BH-powered quantum heat engine. The envisaged effects
substantiate the thermodynamic approach to BH acceleration radiation.
