Ultrafast switching of telecom photon-number states

A crucial component of photonic quantum information processing platforms is the ability to modulate, route, convert, and switch quantum states of light noiselessly with low insertion loss. For instance, a high-speed, low-loss optical switch is crucial for scaling quantum photonic systems that rely on measurement-based feed-forward approaches. Here, we demonstrate ultrafast all-optical switching of heralded photon-number states using the optical Kerr effect in a single-mode fiber. A local birefringence is created by a high-intensity pump pulse at a center wavelength of 1030nm that temporally overlaps with the 1550nm photon-number states in the fiber. By taking advantage of the dispersion profile of commercially available single-mode fibers, we achieve all-optical switching of photon-number states, with up to 6 photons, with a switching resolution of 2.3ps. A switching efficiency of >99% is reached with a signal-to-noise ratio of 32,000.