Extended Data Fig. 1: Device description and characterisation of hybrid sections.
From: Observation of edge and bulk states in a three-site Kitaev chain
a. Zoomed out SEMs of copies of the measured device obtained after deposition of Ohmic contacts, showing the full structure of the superconducting loop. b. Close-up SEM of the finished device, including the full circuit diagram. Bottom left in-set shows a cross-sectional schematic of the device along the channel, adapted from Q.W. (manuscript in preparation), to visualise the order of the three gate layers. Resonators are formed by inductors in combination with a parasitic capacitances to ground, which allows for fast radio-frequency (RF) measurements, used in this work for tuning and characterisation of the system. Voltage sources and current meters are attached to each lead via ≈ 5 kΩ resistors, acting as bias tees, used to obtain the conductance measurements in the main text. Sub-figures (c-h.) show characterisations of the three possible hybrid configurations, after a 1-D channel is formed with the large depletion gates. Schematics on the right display the activated tunneling gates and relevant Ohmic contacts for each row. c. RF-spectroscopy of the Josephson junction formed by the two superconducting fingers at the ends of the loop, as a function of the magnetic field Bz perpendicular to the loop. d Measured current IR with VR = 100 μV, in a wider range of Bz. Fitting the oscillations with a periodic Gaussian function provides an estimate for the flux periodicity (28 μT). e Tunneling spectroscopy of the left SC finger in isolation, as a function of \({V}_{{\rm{ABS}}}^{{\rm{(1)}}}\) applied to the gate covering the left hybrid region. f. Line-trace from (e) at \({V}_{{\rm{ABS}}}^{{\rm{(1)}}}\) = −100 mV, to show the presence of a sub-gap state in the left hybrid. g. Tunneling spectroscopy of the right SC finger in isolation, as a function of the gate covering the right hybrid region (\({V}_{{\rm{ABS}}}^{{\rm{(2)}}}\)). h. Line-trace from (g) at \({V}_{{\rm{ABS}}}^{{\rm{(2)}}}\) = 125 mV to show the presence of a sub-gap state in the right hybrid.
