  The theoretical existence of photon-number-splitting attacks creates a
security loophole for most quantum key distribution (QKD) demonstrations that
use a highly attenuated laser source. Using ultra-low-noise, high-efficiency
transition-edge sensor photodetectors, we have implemented the first version of
a decoy-state protocol that incorporates finite statistics without the use of
Gaussian approximations in a one-way QKD system, enabling the creation of
secure keys immune to photon-number-splitting attacks and highly resistant to
Trojan horse attacks over 107 km of optical fiber.
