Double Upconversion for Superconducting Qubit Control realised using Microstrip Filters

TL;DR

This paper introduces a simplified double upconversion method for superconducting qubit control, reducing hardware calibration needs and successfully demonstrating high-quality qubit tone generation with minimal spurious signals.

Contribution

It presents an economical physical implementation of double upconversion using standard PCB microstrip filters and RF mixers, improving control efficiency for superconducting qubits.

Findings

Achieved over 70dB spurious-free dynamic range in qubit tones.

Successfully controlled a superconducting transmon qubit.

Reduced hardware calibration compared to traditional IQ modulation.

Abstract

Superconducting qubits provide a promising platform for physically realising quantum computers at scale. Such devices require precision control at microwave frequencies. Common practice is to synthesise such control signals using IQ modulation, requiring calibration of a in-phase (I) and quadrature (Q) signals alongside two DC offsets to generate pure tones. This paper presents an economic physical implementation of an alternative method referred to as double upconversion which requires considerably less hardware calibration and physical resources to operate a qubit. A physical circuit was created using standard PCB design techniques for microstrip filters and two common RF mixers. This circuit was then utilised to successfully control a superconducting transmon qubit. When using proper RF shielding, qubit tones were demonstrated with over 70dB of spurious-free dynamic range across the entire operational spectrum of a transmon qubit.