Single-shot readout of spin-orbit-split Andreev doublets: experimental data*

Modern efforts towards constructing exotic superconducting qubits such as Andreev spin qubits and Majorana bound states hinges on spin-orbit coupling. The physics of these unique quantum systems may be explored using the well-developed microwave techniques of circuit QED, which can yield sharp spectral resolution and time-domain information. Here we report on measurements of long InAs-nanowire Josephson junctions embedded in a circuit QED architecture. The Andreev bound state spectrum includes transitions which correspond to the transfer of a single quasiparticle between two spin-orbit-split Andreev doublets. Some of these transitions exhibit large coupling to the on-chip resonator. Thus, fast, time-domain measurement of the many-body state of the junction can be achieved through dispersive readout. In this second part of a joint presentation, we will describe the experimental data and discuss the outlook.