Polarization-Independent Active Switch

Effectively transmitting quantum information in a quantum network necessarily involves switching, delaying and routing the optical signals. Using polarization states to encode quantum information requires a switching mechanism that preserves the polarization of the incoming signal, and switches without introducing unnecessary loss. We use an optical setup that allows the active switching of a pulsed arbitrarily polarized signal by setting the voltage applied to a Pockel's cell. Free-space measurements show that our setup is able to achieve efficiencies of 87-90%, while maintaining extinction ratios of 100:1. Preliminary quantum process tomography measurements show that the router can maintain the purity of any input quantum state at the 99% level when coupled into single-mode fiber.