Integrated cavity parametric amplifier for qubit readout in 3D circuit QED architecture

High-performance qubit readout is essential for quantum information machines as well as for fundamental physics experiments on quantum measurements. In circuit quantum electrodynamics (cQED) systems, superconducting qubits are read out by monitoring the qubit-state-dependent phase shift of a microwave tone, which then passes through a quantum-limited parametric amplifier before being processed by classical electronics. In this configuration, readout efficiency is mainly limited by loss between the readout microwave resonator and the parametric amplifier. Here we introduce a new design in which the latter is placed into the former—a symmetric superconducting artificial "molecule" housed in a 3D readout cavity that contains both the qubit and the quantum-limited parametric amplifier to read it out. This layout should improve the signal-to-noise ratio while minimizing spurious measurement back-action caused by intra-cavity photons. Preliminary results will be presented.