Timons: superconducting gatemon qubits based on proximitized topological insulators*

Superconducting transmon qubits are frontrunners in the race to build a scalable quantum computer. Gatemons are a transmon variant with the metal-oxide Josephson junction replaced by a voltage-controlled semiconductor, eliminating crosstalk and heating from flux-bias currents, and enabling new topologically-protected modes of operation. Gatemons with proximitized III-Vs are difficult to scale [1], or have short relaxation times due to losses in the host substrate [2]. Both require substantial magnetic fields to tune to the topological regime. Here we introduce a new gatemon platform based on V-VI semiconductor (Bi_xSb_1-x)₂Te₃ 3D topological insulators. We use selective area growth and nanostencil lithography on silicon for scalable fabrication of low-loss TI-gatemon (timon) circuits, and explore the prospect of using magnetic dopants to induce topological protection at zero field. Initial results suggest the timon platform is reliable and robust enough for next-generation gatemons [3].

[1] T. W. Larsen, et al., Phys. Rev. Lett. 115, 127001 (2015)
[2] L. Casparis, et al., Nature Nanotech. 13, 915–919 (2018)
[3] T. W. Schmitt, et al., arXiv:2007.04224 (2020)