Development of Superconducting Qubit Circuits to Coherently Probe Majorana Zero Modes Part II: Experimental Results*

A proximitized semiconducting nanowire (NW) with high spin-orbit coupling is one of the most promising candidate systems to achieve a topologically protected qubit. Several proposals for achieving such a qubit use proximitized superconducting islands connected via gate-tunable Josephson junctions [1,2]. When two such islands are tuned to the topological regime the hybridization of the Majorana zero modes at the junction give rise to the fractional Josephson coupling. This additional coupling shows as additional features in the transition spectrum.
Here we perform microwave spectroscopy of NW island-devices with low charging energy using a superconducting λ/2 coplanar waveguide resonator. We study microwave transitions in the presence of in-plane fields large enough to enter the topological regime.

References:
[1] E. Ginossar et al., Nat. Commun, 5, 4772 (2014)
[2] D. Aasen et al, Phys. Rev. X, 6, 031016 (2016)