Operation of Josephson Voltage Standard with Superconducting Shield in Magnetic-Field Environment

We have successfully operated a Josephson voltage standard (JVS) with a superconducting shield in a magnetic-field environment. This study involves mounting a NbN-based JVS chip on a custom-made 12 K stage adjacent to the 4 K stage within a dilution refrigerator. A magnetic field, reaching up to 10 T and generated by a superconducting magnet positioned 73 cm below the JVS chip, is initially reduced by a cancellation coil and further minimized by a superconducting shield comprising Nb, Pb, and permalloy. Consequently, clear Shapiro steps were observed under a magnetic field of approximately 10 T. This achievement marks a significant milestone toward facilitating quantum metrology triangle experiments within a single dilution refrigerator and conducting precise voltage measurements under extreme conditions.