  The Toffoli gate is an essential logic element, which permits implementation
of a reversible processor. It is of relevance both for classical as well as
quantum logics. We propose and theoretically study all-optical implementations
of three-bit and four-bit Toffoli gates by application of adiabatic population
transfer techniques. For a three-bit Toffoli gate we use variants of stimulated
Raman adiabatic passage (STIRAP) processes in a $\Lambda$-type level scheme,
driven by two laser pulses at sufficiently large detunings. For the
implementation of a four-bit Toffoli gate, we apply reversible adiabatic
population transfer in five-level quantum systems, interacting with three laser
pulses. We demonstrate correct all-optical implementation of the truth table of
three-bit and four-bit Toffoli gates. Moreover, we derive conditions for
adiabatic evolution of the population dynamics and robust operation of the
gates.
