Microwave multi-planar package design for superconducting qudit chips with integrated support elements

Superconducting qubits have recently demonstrated quantum supremacy in noisy-intermediate scale processors for practical and scalable quantum information processing. These multi-qubit and multi-dimensional subsystems in planar wafer-scale configurations require innovative solutions in the dense multi-channel drive and readout across many physical and logical superconducting circuits. Unlike conventional microwave packaging for the operational range of 4GHz to 8 GHz, additional challenges with planar dense high-dimensional qudits emerge with maintaining high-fidelity of signals, suppression of spurious modes and crosstalk over closely-spaced frequency channels, and proper thermal control of the qubits and circuits at dilution fridge temperatures of ≈15 mK.

Here we focus on the development of a microwave package from material and geometric choices to designing the resonant cavity and multi-layer interposer to provide an accommodating environment for planar qudit circuits – with high-fidelity control and readout signals while suppressing chip, cavity and interposer-based noisy modes up to 10 GHz while also reducing inter-channel crosstalk in the package. The final segments provide general guidelines to scale the presented microwave package for higher qudit systems.