Extended Data Fig. 1: Cryogenic wiring diagram and device micrographs.
From: Continuous monitoring of a trapped superconducting spin
Optical micrograph e, is of the device on which the presented measurements were performed. Optical micrographs b, c, d, and scanning electron micrograph f, are of an extremely similar (unmeasured) device, the main difference being that the length of the weak link is 750nm instead of 500nm. The microwave readout and drive tones pass through the depicted circuitry a, before being routed through the Δ port of a 180∘ hybrid resulting in differential microwave voltages at the device input. After reaching two coupling capacitors (c), the readout tone was reflected off the differential λ/4 mode of the coplanar strip resonator (red, frequency fr = 9.18843GHz, coupling κc = 2π × 1.23MHz, internal loss κi = 2π × 1.00MHz) and then routed through the depicted amplification chain (a), which was comprised of a SNAIL parametric amplifier (SPA), HEMT, and room-temperature amplifiers. In this circuit, the drive tone creates an ac phase drop across the nanowire (f), which is embedded in the superconducting Φ-bias loop (green) at the end of the resonator (d,e). One edge of the loop connects the two strips of the resonator and thereby forms the shared inductance with the nanowire. We controlled the electrostatic potential in the nanowire weak link (f) with a dc gate (pink, voltage Vg). Gates on the nanowire leads (orange) were used to gain additional electrostatic control, which were biased to the same voltage Vnw = 0.9V for all presented data. To reference the resonator/nanowire island to ground, an additional strip runs between the resonator strips, and connects to a large finger capacitor (purple). This strip does not significantly perturb the resonator’s microwave properties because it resides at the zero voltage point with respect to the resonator’s differential mode.
