  We consider a foundational question in energy harvesting: given a partly
random energy source, is it possible to extract the energy without also
transferring randomness or accepting another thermodynamical cost? We answer
this in the positive, describing scenarios and protocols where in principle
energy is extracted from a field with randomness but without any randomness
being transferred, and without energy dissipation. Such protocols fundamentally
outperform existing methods of rectification which dissipate power, or feedback
demon-like protocols which transfer randomness to the feedback system. The
protocols exploit the possibility of the harvesting system taking several
trajectories that lead to the same final state at a given time. We explain why
these protocols do not violate basic physical principles. A key example
involves the experimentally well-established phenomenon of Rabi oscillations
between energy levels, exploiting the multitude of rotation axes in the state
space that take the lower energy state to the excited state. The quantum system
is deterministically excited to the highest energy level after interacting with
the source for a fixed amount of time, irrespective of the random initial phase
of the external potential.
