But such measurements are notoriously challenging: the instruments used are themselves governed by quantum laws, and their interaction with particles can alter the very properties they are meant to observe.

“The field of quantum measurements is still poorly understood because it has received little attention so far. Until now, research has mainly focused on the states of quantum systems themselves, which feature properties—like entanglement or superposition—that are more directly applicable to areas such as quantum cryptography or quantum computing,” explains Alejandro Pozas Kerstjens, Senior Research and Teaching Assistant in the Department of Applied Physics, Physics Section, at the UNIGE Faculty of Science.