Cryogenic Interface Circuits

This book investigates a range of circuit design techniques to enhance the performance of superconductor-semiconductor interface circuits, essential in cryogenic computing platforms including superconducting high-performance classical computing, quantum computing, digital signal processing, single-photon detection, and neuromorphic computing. Key performance metrics, including power dissipation, output voltage swing, and biasing schemes, are optimized for interface circuits employed in 4 K Josephson-CMOS hybrid memory systems. The authors introduce multi-level output signaling techniques, which increase the data rate of high-speed digital links that transmit data from 4 K cryogenic environments to room-temperature electronics. Lightweight, hardware-efficient error-correction code encoders are also introduced for superconductor-semiconductor interface data links. The authors analyze pertinent hardware security issues, with a focus on power side-channel leakage. A correlation between the internal switching activity of interface circuits and their power dissipation is identified, revealing potential vulnerabilities in both superconducting classical and quantum computing systems. In addition to the security implications, this side-channel leakage is discussed as an alternative mechanism for design-for-testability in SFQ circuits.