Microwave Engineering for Semiconductor Quantum Dots in a cQED Architecture

TL;DR

This paper presents an engineered microwave environment for quantum dots in cQED architectures, achieving high quality factors and low crosstalk through multilayer fabrication and impedance control, enabling advanced quantum dot processing.

Contribution

It introduces a multilayer fabrication approach and impedance tuning to enhance microwave coupling and reduce energy leakage in quantum dot cQED systems, with demonstrated high quality factors.

Findings

Achieved on-chip quality factors of 8140 without explicit filtering.

Demonstrated single electron occupation detection in double and triple dots.

Maintained microwave crosstalk below -20 dB up to 18 GHz.

Abstract

We develop an engineered microwave environment for coupling high Q superconducting resonators to quantum dots using a multilayer fabrication stack for the dot control wiring. Analytic and numerical models are presented to understand how parasitic capacitive coupling to the dot bias leads can result in microwave energy leakage and low resonator quality factors. We show that by controlling the characteristic impedance of the dot bias wiring, on-chip quality factors of 8140 can be attained without the addition of explicit filtering. Using this approach we demonstrate single electron occupation in double and triple dots detected via dipole or quadrupole coupling to a superconducting resonator. Additionally, by using multilayer fabrication we are able to improve ground plane integrity and keep microwave crosstalk below -20 dB out to 18 GHz while maintaining high wire density which will be necessary for future circuit quantum electrodyanmics (cQED) quantum dot processors.