After a phenomenologic description of the Josephson effect, performance data of oscillators, detectors, mixers and parametric amplifiers as well as of integrated memory and logic circuits with Josephson junctions are presented.
Supra-THz heterodyne mixers generally have higher conversion loss compared to the millimetre-wave mixers. Hence, the overall receiver noise temperature becomes increasingly dominated by the first-stage semiconductor low noise amplifier (LNA), which still struggles to achieve quantum-limited noise performance. Here, we aim to develop a Josephson junction travelling wave parametric amplifier (JTWPA) that can achieve high gain over broad bandwidth but with better noise performance to replace these Intermediate Frequency (IF) amplifiers. JTWPAs are typically considered not suitable for astronomical receivers due to their low power handling capability. However, the critical current of the Josephson junctions (JJ) can be easily engineered to match the output power of the front-end detectors. Nevertheless, this may results in the requirement of a higher number of JJs as the junction inductance is in reverse relation with the critical current. Therefore, in this paper, we aim to explore the different design parameters required for developing a JTWPA with a dynamic range compatible for readout a Superconductor-Insulator-Superconductor (SIS) mixer, as an example. Here, we present two JTWPA models that are suitable for the objective, one requiring 3,142 Nb/Al-AlOx/Nb junctions with a maximum gain of 23 dB, and the other with a lower gain at 16 dB but requires only 1,317 JJs. We then compare the SIS receiver noise performance utilising these JTWPAs with that of using a conventional high gain High Electron Mobility Transistor (HEMT) amplifier. We show that we can improve the receiver sensitivity significantly by either cascading two 23 dB gain JTWPA or using a combination of a 16 dB gain JTWPA and a HEMT amplifier. We conclude that the former option more suitable for large detector array applications as it completely replaces the high heat dissipation HEMT amplifiers; while the latter option is favourable at this stage for low pixel count application as it is easier to fabricate a lower number of junctions JTWPA.
Superconductive electronics offers a unique combination of high bandwidth and low power for mission critical hardware such as digital processors at 20 to 100 GHz, microwatt per bit analog to digital converters, large digital switches at multi-Gb/s data rates, and low noise parametric amplifiers. This cryogenic technology, typically operating at a few degrees or a few tens of degrees Kelvin, depends upon the unique physics of superconducting materials such as Nb, NbN, and YBaCuO, and the fundamental circuit element, the Josephson junction (JJ) to create unique architectures of unprecedented design efficiency and performance. These circuits are based on the single flux quantum (SFQ) logic family, a technology that has no parallel in semiconductor electronics. Digital data is transmitted by voltage pulses with amplitude less than 1 mV, but at extremely high speeds. Individual gates have been operated as high as 370 GHz. In this paper, we present a brief overview of superconductive digital technology, describe some recent circuits, and discuss how the challenges to superconductive technology are being met, including the use of multi-chip module (MCM) technology, and the potential use of III-V HBT and HEMT circuits to provide interface drivers and amplifiers, possibly operated cryogenically.
We propose a low-noise and low-power-consumption microwave amplifier using superconductor-insulator-superconductor (SIS) mixers as quasi-particle frequency up- and down-converters pumped by a Josephson array oscillator in the millimeter-wave band. A proof-of-concept study of an amplifier with two W-band waveguide mixers using Nb/Al-AlOx/Nb junctions in a cascade connection demonstrated an average gain of 6 dB and a noise temperature of 12 K from nearly DC to 5 GHz. We also designed and fabricated a Josephson array oscillator at 100 GHz, which consisted of 31 overdamped Josephson junctions placed at each half-wavelength in an Nb microstrip line. The estimated output power of the oscillator was 0.2 μW at 100 GHz, which can be increased by increasing the number of the oscillator junctions. These results suggest that the proposed SIS mixer-based amplifier is suitable for on-chip integrated circuits to be implemented in large-scale multipixel SIS receivers and quantum computers.