Figure 1

(a) Global Optical Microscope view of the Josephson junction chain named Sample 1. This sample has CPW geometry and the chain consists of 384 SQUIDs with total length of 100 μm. Two thin-film capacitors with the sizes 200 μm × 20 μm are fabricated on chip and connected in series to shunt the chain. (b) Optical Microscope image of the center gap together with termination leads. (c) SEM image of the Josephson junction chain named “Sample 1”. The PSC SQUID visible at the center of the chain has smaller junction size (~2 × 95 nm×105 nm, coloured in yellow) and larger loop area (~12×) acting as phase-slip center. Chain SQUIDs (coloured in purple) with larger junction sizes (~2 × 100 nm × 300 nm) are located on either side of the PSC SQUID. SEM image is taken when the beam is tilted ~50° along with the direction of the arrows indicating the weak junctions of the PSC SQUID. (d) Sketch of the tunable-link chain named “Sample 2”. Different than Sample 1, the junction areas are the same for both chain SQUIDs and the tunable-link SQUID in this sample. But the loop area of the big SQUID is approximately twice as the chain SQUIDs. (d) Circuit model of the one-dimensional Josephson junction chain used for the simulations.