science

(...) quenching supercurrents in a superconducting YBa₂Cu₃O₇ thin disc exposed to an external magnetic field. Supercurrents naturally form to expel magnetic fields from superconductors. "By abruptly disrupting these currents using ultrashort laser pulses, we could generate ultrafast magnetic field steps with rise times of approximately one picosecond (...)

Such a magnetic field (change) will propagate (at the speed of light in vacuum) during that time (10^-12^ s) to a distance of about 0.3 millimeter. So, don't go too far away if you want to see that change happened this fast !