High-dimensional Quantum Key Distribution Using Orbital Angular Momentum of Single Photons from a Colloidal Quantum Dot at Room Temperature

High-dimensional quantum key distribution (HDQKD) is a promising avenue toaddress the inherent limitations of basic QKD protocols. However, experimentalrealizations of HDQKD to date have relied on indeterministic photon sourcesthat limit the achievable key rate. In this paper, we demonstrate a fullemulation of a HDQKD system using a single colloidal giant quantum dot (gQD) asa deterministic, compact and room-temperature single-photon source (SPS). Wedemonstrate a practical protocol by encoding information in a high-dimensionalspace (d = 3) of the orbital angular momentum of the photons. Ourexperimental configuration incorporates two spatial light modulators forencoding and decoding the spatial information carried by individual photons.Our experimental demonstration establishes the feasibility of utilizing highradiative quantum yield gQDs as practical SPSs for HDQKD. We also demonstrateexperimentally secure qudit transmission exceeding one secure bit per photon,thus already beating the traditional d=2 QKD capacity.