  Quantum teleportation is an essential quantum operation by which we can
transfer an unknown quantum state to a remote location with the help of quantum
entanglement and classical communication. Since the first experimental
demonstrations using photonic qubits and continuous variables, the distance of
photonic quantum teleportation over free space channels has continued to
increase and has reached >100 km. On the other hand, quantum teleportation over
optical fiber has been challenging, mainly because the multi-fold photon
detection that inevitably accompanies quantum teleportation experiments has
been very inefficient due to the relatively low detection efficiencies of
typical telecom-band single photon detectors. Here, we report efficient quantum
teleportation over optical fiber using four high-detection efficiency
superconducting nanowire superconducting single-photon detectors (SNSPD) based
on MoSi. These SNSPDs make it possible to perform highly-efficient multi-fold
photon measurements, allowing us to confirm that the quantum states of input
photons were successfully teleported over 100 km of fiber.
