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Single-Flux-Quantum Multiplier Circuits for Synthesizing Gigahertz Waveforms With Quantum-Based Accuracy



Manuel C. Castellanos Beltran, David I. Olaya, Adam J. Sirois, Christine A. Donnelly, Paul Dresselhaus, Samuel Benz, Peter F. Hopkins


We designed, simulated, and experimentally demonstrated components for a microwave frequency digital-to-analog converter (DAC) based on rapid single flux quantum (RSFQ) circuits and a superconducting amplifier based on SQUID stacks. These are key components of a self-calibrated programmable waveform reference for communications metrology capable of synthesizing high-speed signals having output with quantum-based accuracy. The amplifier is an SFQ voltage multiplier circuit that consists of a network of SFQ-splitters and SQUID transformers that provides output signals based on quantized pulses. The circuits were fabricated using our Nb/NbxSi1-x/Nb Josephson junction (JJ) fabrication process that produces self-shunted JJs with Nb-doped silicon barriers. In order to demonstrate the quantum-based reproducibility, stability and performance at 4 K, we synthesized single-tone and multi-tone waveforms at gigahertz frequencies and demonstrated their operation over a range of synthesizer and experimental bias parameters. We also propose future circuit designs for achieving higher power, power accuracy, spectral purity, and higher frequencies and discuss the potential limitations.
IEEE Transactions on Applied Superconductivity


Superconducting electronics, Josephson effect, Josephson device fabrication, superconducting integrated circuits, signal synthesis, digital-analog conversion, superconducting microwave devices


Castellanos, M. , Olaya, D. , Sirois, A. , Donnelly, C. , Dresselhaus, P. , Benz, S. and Hopkins, P. (2021), Single-Flux-Quantum Multiplier Circuits for Synthesizing Gigahertz Waveforms With Quantum-Based Accuracy, IEEE Transactions on Applied Superconductivity, [online],, (Accessed July 24, 2024)


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Created February 3, 2021, Updated April 6, 2021