A 0.03 mm2 Inductorless 50 Gb/s Multiplexer for Josephson Arbitrary Waveform Synthesizers

In this paper we present a high-speed 50 Gb/s current mode logic (CML) 2:1 Multiplexer (MUX) for driving of the Josephson Arbitrary Waveform Synthesizers (JAWS). JAWS can be used in quantum physics-related applications. For example, JAWS can be used as a voltage standard in metrology applications or as a reproducible quantum-based microwave signal source to control superconducting qubits in quantum computing. JAWS requires at its input a very long sigma-delta modulated sequence of current pulses, which is translated by the device into a highly accurate quantized analog voltage at its output. In that sense, JAWS can be seen as a quantum-accurate digital-analog converter (DAC). The very long sequence of digital bits is usually divided into several parts and stored in a memory. The parts are read out cyclically, and multiple parallel streams are serialized into a high-speed 50 Gb/s serial data stream using several multiplexer stages, providing the resulted combined control sequence to the JAWS input. The MUX presented in this work is the last stage of a multiplexer chain operating at the highest frequency and interfacing the JAWS. Quantum computers with a large number of qubits require scalable and power-efficient control electronics. To address this concern, we optimized the presented design for low power consumption to fit within a very low available cooling budget. The design is based on a 130 nm SiGe BiCMOS technology and operates from a 3V single supply voltage. The maximum data rate is 50 Gb/s with a 140 mV single-ended voltage swing. This circuit has a miniature core area of 0.03 mm² and a very low power consumption of 10 mW.