Implementing high-efficiency measurement chains for near-quantum-limited measurement of mechanical motion in a superconducting microwave optomechanical circuit.*

Quantum-limited measurement chains are pivotal for many quantum protocols such as real-time feedback or quantum-enhanced metrology. Such measurement chains have been implemented using Josephson parametric amplifiers in qubit control experiments where the control signals are relatively weak. Still, to date, the majority of experiments in the field of microwave optomechanical circuits have been performed with readouts far away from the quantum limit, as implementing such a readout for mechanical motion poses certain challenges: it should feature high gain and bandwidth larger than the frequency of the mechanical oscillator and should allow for strong drives. The results reflecting the actual progress on the experimental implementation of the high-efficiency readout suitable to implement a real-time measurement-based control of a mechanical oscillator in a multi-mode optomechanical circuit will be presented.