  In photonic quantum applications, optical routers are required to handle
single photons with low loss, high speed, and preservation of their quantum
states. Single-photon routing with maintained polarization states is
particularly important for utilizing them as qubits. Here, we demonstrate a
polarization-maintaining electro-optic router compatible with single photons.
Our custom electro-optic modulator is embedded in a configuration of a
Mach-Zehnder interferometer, where each optical component achieves
polarization-maintaining operation. We observe the performance of the router
with 2-4% loss, 20 dB switching extinction ratio, 2.9 ns rise time, and $>$ 99%
polarization process fidelity to an ideal identity operation.
