  Electronic ratchets transduce local spatial asymmetries into directed
currents in the absence of a global drain bias, by rectifying temporal signals
that reside far from thermal equilibrium. We show that the absence of a drain
bias can provide distinct energy advantages for computation, specifically,
reducing static dissipation in a logic circuit. Since the ratchet functions as
a gate voltage-controlled current source, it also potentially reduces the
dynamic dissipation associated with charging/discharging capacitors. In
addition, the unique charging mechanism eliminates timing related constraints
on logic inputs, in principle allowing for adiabatic charging. We calculate the
ratchet currents in classical and quantum limits, and show how a sequence of
ratchets can be cascaded to realize universal Boolean logic.
