Fig. 3: Frequency and Kerr strength for SNAIL-terminated resonator coupled to a qubit.
From: Resolving Fock states near the Kerr-free point of a superconducting resonator
a The frequency of the nonlinear resonator vs. the external magnetic flux through the SNAIL. Blue dots (red curve) are (is) the experimental (fitting) data. By fitting the data to Eq. (3) [red curve], we obtain β = 0.09993 ± 0.00005, well matched with the resistance ratio of the big junction over the small junction 0.104, measured at room temperature, LJ = 629 ± 8 pH and ωr0/2π = 8.87 ± 0.07 GHz. The crossed point from two blacklines indicate the corresponding resonator frequency at the Kerr-free point. b The Kerr-frequency shift per photon, K, vs. the external magnetic flux through the SNAIL calculated from the parameters in (a). The crossed point from two black lines indicates that the Kerr coefficient is zero at Φext = 0.392 Φ0. The green dot at Φext = 0.386 Φ0 is the operating flux point in our work.
