Fig. 2: Reversed Kerr TWPA implementation.

a Nonlinear coefficient g₄ as a function of the external magnetic flux, calculated using the device parameters obtained from the linear characterization (I₀ = 2.19 μA and r = 0.07, see supplementary information). b Circuit schematic of the reversed Kerr TWPA; I₀ is the critical current of the large junction, rI₀ is the critical current of the small junction and C_g is the ground capacitance per unit cell. The device is threaded by a global magnetic field. The alternated loop geometry hence results in an alternated magnetic flux polarity. c Schematic of the reversed Kerr TWPA. The device is fabricated with double angle aluminum Josephson junction array deposition on silicon substrate, followed by atomic layer deposition of dielectric (alumina) and finally by gold top ground deposition⁵¹. A scanning electron microscopy (SEM) image of the meta-material with false coloring to indicate large (blue) and small (orange) junctions forming a SNAIL in the transmission line is shown as a closeup; the superconducting loop area is colored green.