Characterization of Chip Packaging for Multi-Qubit Quantum Processors

Noisy Intermediate-Scale Quantum (NISQ) superconducting hardware are nowadays widely used to demonstrate surface codes algorithm as well as quantum simulators implementation [1,2]. However, despite having achieved single and two-qubit gates with fidelity above the surface code threshold limit [3], further improvement is required to reduce the number of physical qubits that will be required to operate a fault-tolerant quantum computer.

In this talk we present the results from our newest multi-qubit chip packaging solution: QCage.24 [4]. By implementing a recently developed microwave calibration technique operated at 40 mK [5,6] we can assess the reflection and transmission from the fridge wiring interface. We demonstrate reflection levels below 30 dB in the 4 ­– 8 GHz frequency bandwidth. Furthermore, by knowing the transfer function we simulated gate fidelities with four orders of magnitude improvement compared to non-optimized chip packaging solution (i.e. reflection values in the order of 15 dB).

[1] Krinner, S. et al., Nature 605, 669 (2022)

[2] Mi, X. et al., Nature 601, 531 (2022)

[3] Kjaergaard, M. et al., Annual Review of Condensed Matter Physics 11, 369 (2020)

[4] https://qdevil.com/qcage-microwave-cavity-sample-holder/

[5] Wang, H. et al., Quantum Sci.Technol. 6, 035015 (2021)

[6] Simbierowicz, S. et al., Applied Physics Letters 120, 054004 (2022)