  We propose a high-dimensional quantum key distribution (QKD) protocol that
employs temporal correlations of entangled photons. The security of the
protocol relies on measurements by Alice and Bob in one of two conjugate bases,
implemented using dispersive optics. We show that this dispersion-based
approach is secure against general coherent attacks. The protocol is
additionally compatible with standard fiber telecommunications channels and
wavelength division multiplexers. We offer multiple implementations to enhance
the transmission rate and describe a heralded qudit source that is easy to
implement and enables secret-key generation at up to 100 Mbps at over 2 bits
per photon.
