We have designed a tunable nonlinear resonator terminated by a SNAIL (Superconducting Nonlinear Asymmetric Inductive eLement). Such a device possesses a Kerr-free point in which the external magnetic flux allows to suppress the Kerr interaction. We have excited photons near this Kerr-free point and characterized the device using a transmon qubit. The excitation spectrum of the qubit allows to observe photon-number-dependent frequency shifts about nine times larger than the qubit linewidth. Our study demonstrates a compact integrated platform for continuous-variable quantum processing that combines large couplings, considerable relaxation times and excellent control over the photon mode structure in the microwave domain.

我们设计了一种由 SNAIL（超导非线性不对称电感元件）端接的可调谐非线性谐振器。这种器件具有无克尔点，其中外部磁通量可以抑制克尔相互作用。我们在这个无克尔点附近激发了光子，并使用传输量子位来表征该设备。量子位的激发光谱允许观察与光子数相关的频移，该频移大约是量子位线宽的九倍。我们的研究展示了一个用于连续可变量子处理的紧凑集成平台，该平台结合了大耦合、相当大的弛豫时间和对微波域中光子模式结构的出色控制。