Measurement Strategies A superconducting bosonic qubit is typically based on a low-loss, linear microwave resonator as the bosonic quantum memory. This resonator is coupled to one or more nonlinear superconducting Josephson circuit elements to form ancillary modes that enable the control and measurement of the linear quantum memory. Candidates of the bosonic quantum memory include superconducting microwave electromagnetic resonators, as well as micromechanical oscillators and collective spin excitation modes. The ancillary mode(s) can be provided by a superconducting qubit (e.g., transmon, fluxonium, etc.) or other quantum-limited Josephson parametric devices. The ancilla qubit has its separate control and measurement circuitry, including a microwave readout resonator. Setups of all sizes are controlled through the LabOne Q software, providing hardware abstraction, an experiment control framework, and an interface to higher software layers. Zurich Instruments' solutions provide key features that particularly benefit bosonic qubit experiments in the following experimental methods: System characterization and calibration - Fast and parallel spectroscopy and coherence time measurements of microwave resonators and ancilla qubits - Fast and accurate magnetic flux control of flux-tunable ancilla qubits or Josephson parametric devices using the HDAWG - Efficient system calibration orchestrated and automated by the quantum control software framework LabOne Q - High-purity control signal generation from DC to 8.5 GHz with a direct extension to higher frequencies using external microwave mixers Quantum memory state preparation, control, and tomography - High-density arbitrary-wave signal synthesis at microwave frequencies for both the bosonic quantum memory and the ancilla qubit: * State-of-the-art spurious-free dynamic range (SFDR) achieved through the double-superheterodyne frequency conversion technique * Temperature-stable microwave analog front end free of IQ-mixer calibration * Memory-efficient waveform programming and upload - Stable initial phase difference between multiple output and input channels at arbitrary frequencies for phase coherent microwave drives and parametric measurement of nonlinear quantum devices Measurement-based quantum error correction - Projective error syndrome measurement of the bosonic quantum memory via mapping the error syndrome operator to the ancilla qubit state using microwave pulses, followed by the high-fidelity single-shot readout of the ancilla qubit Remote quantum entanglement and communication - Quantum state transfer between standing microwave photons in the bosonic memory and flying photons in the communication channel using microwave pulses generated by the SHFQC
