An On-Chip Picoampere-Level Leakage Current Sensor for Quantum Processors in 22-nm FD-SOI CMOS

In this article, we present an embedded picoampere-level leakage current sensor of low hardware complexity for quantum computing applications. It senses a leakage current on capacitors comprising a capacitive DAC (CDAC) intended for the control of energy confinement levels and quantum states of a nearby quantum dot structure integrated on the same die. As the quantum states exhibit an exponential sensitivity to the control voltages, any changes in the output voltage of the CDAC due to noise, ripples, or leakage current should be monitored and characterized accurately. For this purpose, we exploit a 1-bit continuous-time comparator to digitize the slope of the CDAC output voltage due to the leakage current. The proposed system occupies 0.013 mm and measures the leakage current over varied temperature from 3.8 K to 270 K. The average leakage current of the CDAC at 3.8 K was measured at 3.57 pA.