Cryogenic CMOS Low-Noise N-Path Amplifier for Spin Qubit RF-Reflectometry Readout

Abstract

This paper discusses a system for reading the fundamental unit of a quantum computer, the qubit, with a focus on silicon-based spin qubits. Specifically, a comparison and analysis of two methods, the DC-readout method and the RF- reflectometry method, are presented. The relevant circuits designed for these methods are also introduced. In particular, a Noise Cancellation Low Noise Amplifier (NC-LNA) is designed, specialized for on-chip implementation with a wide frequency tuning range. Additionally, an Off-Chip Noise Matching Low Noise Amplifier (OCM-LNA) capable of excellent noise performance and low-power design is introduced. Furthermore, circuits leveraging N-Path technology are designed, demonstrating superior selectivity, tunability, and low-noise characteristics. Ultimately, PCB and fixed plate designs are implemented to enable cryogenic measurements. The system achieves a 24dB S21 gain and 1.88dB noise figure at 300K, as well as a 30dB S21 gain at 77K.