Can a qudit carry more information than a dit?

Abstract

Conventional wisdom suggests that within a fixed preparation-measurement setup, a qubit system offers no advantage over a bit. This indeed holds true when considering the standard communication and the famous Holevo bound then formalizes the statement that one qubit can encode at most one bit of information. However, there exist subtle differences between these two physical systems that, when properly exploited, can be converted into practical applications. We begin by discussing the similarities between qudits and dits as information carriers. Then we recall a general framework for communication tasks and review some differences that qudits and dits have. In the end, we present a simple communication application that utilizes the quantum character of the qubit.