Engineering a bosonic CZ gate between two superconducting cavities

Bosonic cQED systems are a promising platform for hardware-efficient and error-correctable quantum information processing due to the infinite Hilbert space of superconducting cavities. To achieve universal control, multiple cavity modes are typically coupled to an auxiliary qubit, whose discrete transitions are used to enact logical gates. This ultimately limits the quality of the gates performed on the bosonic mode, due to the shorter qubit coherence times.

Here, we present the latest results and updates of a CZ gate for different rotationally-symmetric codes that relies only on the non-linearity provided by the Josephson junction, without actively populating the excited energy levels of the qubit. Such a gate can also be applied to detect for photon loss in a fault-tolerant manner.