  Quantum key distribution (QKD) enables unconditionally secure communication
guaranteed by the laws of physics. The last decades have seen tremendous
efforts in making this technology feasible under real-life conditions, with
implementations bridging ever longer distances and creating ever higher secure
key rates. Readily deployed glass fiber connections are a natural choice for
distributing the single photons necessary for QKD both in intra- and intercity
links. Any fiber-based implementation however experiences chromatic dispersion
which deteriorates temporal detection precision. This ultimately limits maximum
distance and achievable key rate of such QKD systems. In this work, we address
this limitation to both maximum distance and key rate and present an effective
and easy-to-implement method to overcome chromatic dispersion effects. By
exploiting the entangled photons' frequency correlations, we make use of
nonlocal dispersion compensation to improve the photons' temporal correlations.
Our experiment is the first implementation utilizing the inherently
quantum-mechanical effect of nonlocal dispersion compensation for QKD in this
way. We experimentally show an increase in key rate from 6.1 to 228.3 bits/s
over 6.46 km of telecom fiber. Our approach is extendable to arbitrary fiber
lengths and dispersion values, resulting in substantially increased key rates
and even enabling QKD in the first place where strong dispersion would
otherwise frustrate key extraction at all.
