Dispersive detection of a charge qubit with a broadband high-impedance quantum-Hall plasmon resonator

TL;DR

This paper demonstrates dispersive detection of a charge qubit using a broadband high-impedance quantum-Hall plasmon resonator, leveraging topological edge modes to enhance cQED interactions and enable qubit spectroscopy.

Contribution

It introduces a novel high-impedance plasmon resonator based on quantum Hall edge modes for dispersive qubit detection, expanding the platform for cQED applications.

Findings

High-impedance quantum-Hall plasmon resonator enables dispersive qubit detection.

Broad bandwidth allows effective qubit spectroscopy.

Topological edge modes facilitate enhanced light-matter interactions.

Abstract

Cavity quantum electrodynamics (cQED) provides strong light-matter interactions that can be used for manipulating and detecting quantum states. The interaction can be enhanced by increasing the resonator's impedance, while approaching the quantum impedance ($h/e^2$) remains challenging. Edge plasmons emergent as chiral bosonic modes in the quantum Hall channels provide high quantized impedance of $h/ \nu e^2$ that can exceed 10 k$\Omega$ for the Landau-level filling factor $\nu \leq 2$, well beyond the impedance of free space. Here, we apply such a high-impedance plasmon mode in a quantum-Hall plasmon resonator to demonstrate dispersive detection of a nearby charge qubit formed in a double quantum dot. The phase shift in microwave transmission through the plasmon resonator follows the dispersive shift associated with the qubit state in agreement with the cQED theory. The high impedance allows us to perform dispersive detection of qubit spectroscopy with a plasmon resonator having a broad bandwidth. Leveraging these topological edge modes, our results establish two-dimensional topological insulators as a new platform of cQED.