Matteo Bina - Università di MIlano

Designing multimode Gaussian and non-Gaussian operations with superconducting circuits

Universal quantum computation is a key requirement for quantum computers, as it unlocks the full landscape of possible operations.

While qubit platforms have matured to the point of demonstrating universal gate sets experimentally, in continuous-variable systems the non-Gaussian operations required to reach universality remain an open and active challenge. Superconducting-circuit platforms, unlike quantum-optical setups, offer a rich toolbox for engineering effective non-linear interactions, enabling non-Gaussian operations such as the cubic-phase gate and three-mode interaction gates. In this work, we present the Asymmetrically Threaded SNAIL (ATS), a superconducting non-linear element acting as a tunable coupler between multiple linear resonators — up to four or five modes simultaneously. This multimode architecture gives rise to a rich set of both Gaussian and non-Gaussian interactions, including single- and two-mode squeezing, beam-splitter coupling, tri-squeezing and three-mode squeezing interactions. The large accessible parameter space allows for the identification of distinct operating points, enabling the selective activation of desired interactions through targeted driving, thus providing a high degree of tunability.