Chip Packaging with Improved Microwave Performance for Superconducting Quantum Circuits

Chip packaging has become a limiting factor for achieving long lived coherent operation of superconducting quantum circuits. The local microwave environment represents a source for loss and decoherence that needs to be considered in the packaging design.[1] Quantum Machines and QDevil have developed a chip packaging solution called QCage, optimized for low loss and decoherence, reflection free transmission and free from resonances.[2,3] This solution has been adopted by several scientific laboratories who saw vast improvements compared to packaging solutions developed by themselves. In an extensive study of losses in superconducting resonators by the Houck lab at Princeton University, quality factors as high as 200 million were reached in the QCage.24 sample holder.[4] These results indicate that the residual microwave losses in the packaging are only contributing to relaxation on time-scales of tens of milliseconds, much longer than the best superconducting qubits that were demonstrated to date.[5] In another study of quasiparticle dynamics in hybrid semiconductor/superconductor Josephson junctions by Shabani lab at New York University,suppression of quasiparticle poisoning was observed.[6] This was in part attributed to the careful EMC shielding of the QCage design.