On- and off-chip superconducting resonators for hybrid quantum devices on planar germanium.

Superconducting resonators coupled to arrays of quantum dots provide a reconfigurable testbed for quantum technology, as well as quantum simulation and many-body physics. Recent work, showing proximitization of quantum dots in planar germanium, has shown the potential for Andreev states and Andreev spin qubits (ASQs) in planar germanium [1], which could form one of the main building blocks for a superconductor-semiconductor hybrid platform. ASQs could perform multiple roles in such a platform, for example as a coupler or as a method to enhance readout for semiconductor spin qubits [2], both potentially co-integrated in a germanium heterostructure. Such heterogeneous processor architectures could alleviate challenges for both qubit modalities and aid scaling.

Here, we present our work focusing on the performance of superconducting resonators integrated with a planar germanium heterostructure, with an emphasis on on-chip and off-chip resonator engineering, to sense primitive superconducting circuits comprising a gated germanium weak link.

 

[1] L. Lakic et al., “A quantum dot in germanium proximitized by a superconductor,” Nature Materials, vol. 24, pp. 552–558, 2025.

[2] M. Jakob et al., “Fast readout of quantum dot spin qubits via Andreev spins,” arXiv preprint arXiv:2506.19762, 2025.