High-resolution imaging of magnetic fields of banknote anti-counterfeiting strip using fiber diamond probe

Abstract

Counterfeiting of modern banknotes poses a significant challenge, prompting the use of various preventive measures. One such measure is the magnetic anti-counterfeiting strip. However, due to its inherent weak magnetic properties, visualizing its magnetic distribution has been a longstanding challenge. In this work, we introduce an innovative method by using a fiber optic diamond probe, a highly sensitive quantum sensor designed specifically for detecting extremely weak magnetic fields. We employ this probe to achieve high-resolution imaging of the magnetic fields associated with the RMB 50 denomination anti-counterfeiting strip. Additionally, we conduct computer simulations by using COMSOL Multiphysics software to deduce the potential geometric characteristics and material composition of the magnetic region within the anti-counterfeiting strip. The findings and method presented in this study hold broader significance, extending the RMB 50 denomination to various denominations of the Chinese currency and other items that employ magnetic anti-counterfeiting strips. These advances have the potential to significantly improve and promote security measures in order to prevent the banknotes from being counterfeited.