Two Volt Josephson Arbitrary Waveform Synthesizer Using Wilkinson Dividers
Nathan E. Flowers-Jacobs, Anna E. Fox, Paul D. Dresselhaus, Robert E. Schwall, Samuel P. Benz
The root-mean-square (rms) output voltage of the NIST Josephson arbitrary waveform synthesizer (JAWS) has been doubled from 1 V to a record 2 V by combining two new 1 V chips on a cryocooler. This higher voltage will improve calibrations of ac thermal voltage converters and precision voltage measurements that require state-of-the-art quantum accuracy, stability, and signal-to-noise. We achieved this increase in output voltage by use of four on-chip Wilkinson dividers and eight inside-outside dc blocks, which enable biasing of eight Josephson junction (JJ) arrays with high-speed inputs from only four high-speed pulse generator channels. This approach halves the number of pulse generator channels required in future JAWS systems. We also implemented on-chip superconducting interconnects between JJ arrays, which reduces systematic errors and enables a new modular chip package. Finally, we demonstrate a new technique for measuring and visualizing the operating current range that reduces the measurement time by almost two orders of magnitude and reveals the relationship between distortion in the output waveform and incorrectly produced pulse sequences.