Quantum Current Sensor Integrating Quantum Anomalous Hall and Josephson Effects*

Following the International System of Units (SI) redefinition, the units volt and ohm are directly realized via quantum-based standards (the Programmable Josephson Voltage Standard (PJVS) and the Quantum Hall Resistance Standard (QHRS), respectively). Direct realization of the ampere is then achievable through application of Ohm’s Law. However, direct integration of the PJVS and QHRS is challenging due to their vastly different magnetic field requirements. By leveraging the zero-field quantization of a quantum anomalous Hall (QAH) resistor in conjunction with a PJVS, we have demonstrated a direct realization of the Ampere with a quantum current sensor (QCS) in a single cryostat, precisely determining current over the range (9.33–252) nA. QCS accuracy was assessed by comparison to an indirect Ohm’s law measurement of the same current source, using both the QAH resistor and a PJVS-calibrated digital multimeter. The closest agreement, (1.46 +/- 4.28) x 10^-6 A/A, was found at 83.9 nA. In this talk, I will discuss the direct and indirect measurement results, as well as the integration of the QAH resistor and PJVS in a single cryostat.