  Quantum optical Fredkin gate is an indispensable resource for networkable
quantum applications. Its performance in practical implementations, however, is
limited fundamentally by the inherent quantum fluctuations of the pump waves.
We demonstrate a method to overcome this drawback by exploiting stimulated
Raman scattering in fiber-based implementations. Using a Sagnac fiber-loop
switch as a specific example, we show that high switching contrast can be
maintained even in the presence of significant pump fluctuations. This unique
feature of self-stabilization, together with high-speed and low-loss
performance of such devices, point to a viable technology for practical quantum
communications.
