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The two main challenges to operating a programmable Josephson voltage standard (PJVS) on a cryocooler are the available cooling power and the temperature oscillations of the cold head. We overcame these challenges and successfully operated a PJVS circuit on a cryocooler by employing one supercritical helium buffer that damps the temperature oscillations, developing a new cryogenic package that increases the thermal conductivity between the chip and the cold head, and increasing overall device performance with fabrication improvements. A 1.32 mA step width of the quantized voltage produced with all of the subarrays of the PJVS circuit biased was achieved at an operating temperature of 4.3 K. The quantum accuracy of the PJVS is maintained at temperatures up to 4.8 K. This result was obtained with a cryocooler that employs a 3 kW water-cooled compressor to produce at the chip about 270 mW of net cooling power at 4.3 K.11

Contribution of the U.S. government, not subject to copyright. [ABSTRACT FROM PUBLISHER]

A quantum-accurate waveform with an rms output amplitude of 1 V has been synthesized for the first time. This fourfold increase in voltage over previous systems was achieved through developments and improvements in bias electronics, pulse-bias techniques, Josephson junction array circuit fabrication, and packaging. A recently described ac-coupled bipolar pulse-bias technique was used to bias a superconducting integrated circuit with 25 600 junctions, which are equally divided into four series-connected arrays, into the second quantum state. We describe these advancements and present the measured 1 V spectra for 2 Hz and 10 Hz sine waves that remained quantized over a 0.4 mA current range. We also demonstrate a 2 kHz sine wave produced with another bias technique that requires no compensation current and remains quantized at an rms voltage of 128 mV over a 1 mA current range. Increasing the clock frequency to 19 GHz also allowed us to achieve a maximum rms output voltage for a single array of 330 mV. [ABSTRACT FROM PUBLISHER]

A quantum-accurate waveform with an rms output amplitude of 1 V has been synthesized for the first time. This fourfold increase in voltage over previous systems was achieved through developments and improvements in bias electronics, pulse-bias techniques, Josephson junction array circuit fabrication, and packaging. A recently described ac-coupled bipolar pulse-bias technique was used to bias a superconducting integrated circuit with 25 600 junctions, which are equally divided into four series-connected arrays, into the second quantum state. We describe these advancements and present the measured 1 V spectra for 2 Hz and 10 Hz sine waves that remained quantized over a 0.4 mA current range. We also demonstrate a 2 kHz sine wave produced with another bias technique that requires no compensation current and remains quantized at an rms voltage of 128 mV over a 1 mA current range. Increasing the clock frequency to 19 GHz also allowed us to achieve a maximum rms output voltage for a single array of 330 mV. [ABSTRACT FROM PUBLISHER]