Mesoscopic physics is the study of systems ranging in size from nanoscale to microns. A major focus in mesoscopic physics is studying the quantum nature of electrons and associated correlated effects. One way to do that is by measuring “shot noise,” a noise originating from the discrete nature of electrons. Recently, researchers from The University of Tokyo and NTT Corporation published a review in the Journal of the Physical Society of Japan, detailing advances in shot noise measurements in mesoscopic systems.

Shot noise is often too small to be measured using commercial ammeters, and therefore, requires special experimental techniques for its quantitative evaluation. In their review, the researchers introduce and discuss the characteristics of several measurement techniques as well as explain the theoretical framework to calculate the shot noise.

Shot noise studies have revealed unique information about a system modeled within a single-particle picture. For example, the measurements enable us to evaluate the spin polarization of an electronic current flowing through a mesoscopic solid-state device, such as a quantum point contact. Furthermore, they can be used to explore the quantum Hall effect breakdown, tunnel junction devices, correlated electron transport through quantum dots, and Fermion quantum optics.

Another fascinating aspect of shot noise measurements is that they can also be used to study quantum liquids. In fact, physical phenomena such as the Kondo effect, the fractional quantum Hall effect, and superconductivity show their peculiarity in shot noise properties as well as conductance. Additionally, shot noise could help detect exotic particles like Majorana fermions and non-Abelian anyons that could help us create a fault-tolerant topological quantum computer.

All in all, understanding shot noise is critical not only to the development of quantum physics but also to new technologies.