Speaker
Description
Quantum key distribution (QKD) protocols take at least two advantages from high-dimensional (HD) systems: the secret key rate scaling as the dimension and the opportunity of exploiting more than two mutually unbiased bases (MUBs). Indeed, if the dimension d of the system is a prime power, then d+1 MUBs exist. Here, we retrieve analytic key rates for a BBM92-like protocol, where the dimension of the Hilbert space is generic and every allowed number m of MUBs is considered. In the limit of infinite number of rounds, we show that both the key rate and the maximum tolerable error rate increase as m increases. In the finite-key scenario, we retrieve upper bounds on key rates secure against collective and coherent attacks. We find the number of MUBs maximizing the key rate, which, unexpectedly, is not the largest allowed.
