Inductances in Superconducting Circuits

B. V. Vasiliev, V. G. Simkin

C. Fourie, Romain Collot, Pascal Febvre +3 more

Hao Li, Jianshe Liu, Han Cai +4 more

High energy-efficient superconducting circuits are increasingly desirable for information technology. Negative-inductance superconducting quantum interference device (nSQUID) is considered to have the capability of approaching the physical limit of irreversible computing. Superconducting coplanar waveguide (CPW) resonator of high quality factor Q is widely used for detecting extremely small signals. To measure the energy dissipation in nSQUID, we have designed and fabricated an nSQUID with its common mode flux control inductively coupled to a superconducting CPW resonator. The energy dissipation can be obtained from the changes in transmission spectra of the coupled circuit at different input powers. Low temperature experimental results at 1.07 K show that the bit operation energy in nSQUID operating at 2.19 GHz is about 1.38 zJ.

Seong Hyeon Park, Gahyun Choi, Eunjong Kim +6 more

We propose an improved method for quantizing superconducting circuits that incorporates material- and geometry-dependent kinetic inductance. Our approach models thin superconducting films as equivalent reactive boundary elements, seamlessly integrating into the conventional circuit quantization framework without adding significant computational complexity. As a proof of concept, we experimentally verify our method using planar superconducting quantum devices made of 35-nm-thick disordered niobium films, known to exhibit large kinetic inductance values. We demonstrate significantly improved accuracy in predicting the Hamiltonian based solely on the chip layout and material properties of superconducting films and Josephson junctions. Specifically, conventional methods exhibit average errors of 5.4% in mode frequencies and 41% in cross-Kerr shift frequencies, while our method reduces the errors to 1.1% and 11%, respectively. Our method enables systematic studies of superconducting devices based on disordered thin films or compact, fine-pitched elements and, more broadly, facilitates the precise engineering of superconducting quantum circuits at scale.

Gleb Krylov, Eby G. Friedman

Superconductive niobium-based circuits is a promising energy efficient beyond-CMOS technology that can supplement or replace existing large scale CMOS systems. Modern superconductive circuits utilize more than ten metal layers for gates and interconnect. Many sources of inductive coupling noise exist within this environment. Superconductive circuits are particularly vulnerable to inductive coupling, as the operation of the logic gates and flip flops depends on precise bias conditions, and the signal magnitude is relatively small. These inductive coupling sources are characterized, and the effects of inductive coupling noise in different circuit structures are described. Guidelines to mitigate the deleterious effects of coupling noise are presented.

Marric Stephens