Toward high-fidelity inter-chip entanglement between superconducting qubits

Modular quantum networks are a promising approach for scaling superconducting quantum processors, due to their potential to avoid crosstalk and to scale beyond a single wafer. An outstanding challenge for the realization of such networks is to achieve high-fidelity inter-chip entangling gates. Inspired by previous results [1-3], we present a modular hardware scheme for performing gates between superconducting transmon qubits on separated chips. We have engineered a low loss, de-mateable superconducting cable connection that we aim to use as a ‘quantum bus’. Combined with parametric drives this approach can achieve high fidelity gates between the qubits, for instance through driving a virtual Raman process. With measured bus quality factors in excess of 100,000 and demonstrated sideband transition frequencies up to 10 MHz, our experimental data suggest that a gate infidelity below 1% in less than a microsecond is within reach. Our inter-chip connection design could thus serve as a key component in a modular, multi-wafer superconducting quantum computer.



[1]. N. Leung et al., Npj Quantum Information 5, no. 1 (February 15, 2019): 1–5.

[2]. Youpeng Zhong et al., Nature 590, no. 7847 (February 2021): 571–75.

[3]. Luke D. Burkhart et al., PRX Quantum 2, no. 3 (August 5, 2021): 030321.