Encoding mutually unbiased bases in orbital angular momentum for quantum key distribution

Abstract

We encode mutually unbiased bases (MUBs) using the higher-dimensional orbital angular momentum (OAM) degree of freedom associated with optical fields. We illustrate how these states are encoded with the use of a spatial light modulator (SLM). We demonstrate how (d+1)-mutually unbiased measurements can be made in both a classical prepare-and measure scheme and on a pair of entangled photons. In the entanglement-based scheme we perform mutual unbiased measurements for dimensions ranging from d = 2 to 5. The calculation of the average error rate, mutual information and secret key rate show an increase in information capacity as well as higher generation rates as the dimension increases.