Compact RSFQ microwave pulse generator based on an integrated RF module for controlling superconducting qubits

Abstract

An on-chip superconducting microwave pulse generator (MPG), incorporating rapid single-flux-quantum (RSFQ) logic gates and passive radio frequency (RF) components, is an energy-efficient solution for controlling superconducting quantum bits (qubits). Traditional RSFQ MPG designs, however, suffer from a large footprint as multiple RF components (including impedance matching networks, filters, etc.) are separately implemented one after another. In this Letter, we propose a compact on-chip MPG by introducing an integrated RF module. Using a generalized filter synthesis technique, the integrated RF module combines the functionalities of impedance matching and bandpass filtering as a single inductor-capacitor (LC) lumped network. Plenty of circuit elements can, thus, be saved, and the resultant LC network is applicable to both real and complex terminal impedance cases. For validation, a superconducting MPG adopting a fourth-order, 5 GHz centered, 100 MHz bandwidth integrated RF module is designed and fabricated, whose correct operations are confirmed through both simulation and measurement. These results raise the availability of controlling large-scale quantum systems by low-power superconductor technology in the future.