Quantum signals and circuits (continued)

In computer science, the notion of the bit as an elementary unit of information is often discussed in abstract terms, dissociated from a particular implementation, for example when dealing with Boolean operations. This is justified by the universality of most algorithms and communication protocols, which are largely independent of representation details. However, when it comes to the ultimate limits of information processing, and in particular characteristics such as throughput, data volume, energy consumption, latency, etc., the physical nature of the information-carrying degrees of freedom and their mutual interactions become crucial. In this lecture, we explore the physics of electronic devices and systems that process information at the most elementary level : one and zero are represented by the presence and absence of an excitation quantum of electromagnetic fields in the circuit. This year's lessons dealt with situations where the circuit's processing of the quantum signal is weakly out-of-equilibrium.