We present a new implementation of the BB84 quantum key distribution protocol that employs a d-dimensional Hilbert space spanned by spatial modes of the propagating beam that have a definite value of orbital angular momentum. Each photon carries log d bits of information, increasing the key generation rate of the protocol. The states used in the transmission part of the protocol are invariant u...

The recently proposed phase-matching quantum key distribution offers means to overcome the linear rate-transmittance bound. Since information is encoded onto phases of coherent states, misalignment between two remote reference frames would yield errors and significantly degrade generation rate from ideal case. In this work, we propose a reference-frame-independent design by introducing high-dim...