Microwave probing of flux-tunable topological insulator-based Josephson quantum circuits*

Topological superconductivity and Majorana zero modes (MZMs) are predicted to emerge in hybrid devices comprising s-wave superconductors (S) and topological insulators (TIs). Signatures of MZMs include zero-bias conductance peaks in tunnelling spectroscopy of vortex cores and the fractional Josephson effect in S-TI-S Josephson junctions. Here we explore how S-TI-S junctions integrated with superconducting microwave circuits can be used to detect MZMs in the microwave absorption spectrum probed using circuit quantum electrodynamics (cQED). We perform tight-binding simulations to study how the energy-phase relation of MZMs impacts the cQED response of flux-tuneable circuits and report the latest experimental progress towards realising such devices using V-VI semiconductor (Bi_xSb_1-x)₂Te₃ topological insulators.