Active Manipulation of Trapped Flux in Nb Chip at a Single Vortex Level (2025)

Trapped magnetic flux has been a long-standing problem in superconducting digital and quantum circuits, significantly affecting their reliability and limiting practical applications. Mitigation techniques like integrating moat structures into circuit layouts and increasing magnetic shielding have been in use to improve the probability of an accurate circuit operation. However, none of the methods can reliably and deterministically achieve the desired flux-free state of superconducting circuits. Active flux management can potentially solve this problem by the removal of the trapped flux from the relevant circuit areas on a chip. Here, we report numerical modelling and experimental scanning SQUID imaging results showing flux manipulation on the single vortex level using a network of pulsed electric lines in a test superconducting single layer circuit. We demonstrate the effect of vortex sweeping in areas with control lines as well as sweeping of vortices into moats via Lorentz force mechanism. This method can potentially be expanded to larger and more sophisticated digital and quantum chips.