QUANTUM LIMITS TO ALL-OPTICAL SWITCHING IN THE NONLINEAR MACH-ZEHNDER INTERFEROMETER

A Mach-Zehnder interferometer with a nonlinear medium in each arm is treated as an all-optical switching device. In a classical treatment, the interferometer can, in principle, operate as an ideal switch, but quantization of the electromagnetic fields limits the switching capability. In this treatment we illustrate the fundamental quantum limits that apply to switching in all-optical devices by studying the nonlinear Mach-Zehnder interferometer. In particular the input states are assumed to be coherent states and the reduction in the quality of the switching device is discussed.