Towards Fault Tolerant Joint Stabilizer Measurements for Bosonic Qubits: Part 2*

Previously it was demonstrated that a fault tolerant parity measurement could be performed on Bosonic qubits[1]. In this scheme transmon ancilla errors do not propagate onto the logical qubit during the measurement. We extend this protocol to implement a fault tolerant joint-parity measurement on two logical qubits housed in cavities, serving as a measurement of the ZZ stabilizer. Our scheme requires only a switchable beamsplitter interaction between the cavities and an ancilla transmon coupled to just one of the cavities, reducing the need for complicated chi-matching requirements. We present preliminary experimental data demonstrating the protocol in a package containing two 3D stub cavities with beamsplitter couplings actuated by pumping a 3-wave-mixing element. 

[1] Rosenblum Science (2019)