Quantum optical Fredkin gate

A simple optical model to realize a reversible, potentially error-free logic gate---a Fredkin gate---is discussed. The device dissipates no energy and makes use of the Kerr nonlinearity to produce intensity-dependent phase shifts. The analysis shows that quantum mechanics permits the operation of error-free logic gates which dissipate no energy. However, even though the device is nondissipative, error-free performance only occurs under particular operating conditions.