Towards a 2D tantalum Kerr-cat qubit*

Increasing the coherence time of superconducting qubits will enable error-corrected multi-qubit processors that can perform meaningful computations. To improve coherence, advances in qubit encoding and qubit fabrication could independently contribute. The recent Kerr-cat qubit, where the logical qubit is encoded in cat states of a capacitively shunted flux qubit with a 3D readout cavity [1], significantly reduces phase-flip error compared to the standard encoding scheme using Fock states. Separately, using tantalum results in record coherence times in conventional 2D transmon qubits [2,3]. Here we present preliminary work towards a 2D tantalum Kerr-cat qubit, combining these two developments.

[1] Grimm et al., Nature 584 (2020)

[2] Place et al., Nature Comms. 12:1779 (2021)

[3] Wang et al., https://arxiv.org/abs/2105.09890