Gate reflectometry in a minimal Kitaev chain device

TL;DR

This paper demonstrates that RF gate reflectometry can effectively probe charge states, interdot coupling, and parity dynamics in a minimal Kitaev chain device, advancing the understanding of Majorana qubits.

Contribution

It introduces the use of gate reflectometry to distinguish key processes in a Kitaev chain and shows its effectiveness even when the system is decoupled from leads.

Findings

Gate reflectometry resolves charge stability diagrams.

It distinguishes elastic cotunneling from crossed-Andreev reflection.

Quantum capacitance signals indicate parity switching.

Abstract

Hybrid quantum dot (QD)-superconductor system can be used to realize Majorana zero modes in artificial Kitaev chains. These chains provide a promising platform for the realization of Majorana qubits. Radio-frequency (RF) gate reflectometry is a fast, non-invasive, and sensitive technique that can be used to read out such qubits. In this work, we use gate reflectometry to probe two QDs coupled via a semiconductor-superconductor hybrid segment. We demonstrate that gate sensing can resolve charge stability diagrams and clearly distinguish between elastic cotunneling and crossed-Andreev reflection, the two key processes that allow one to form a Kitaev chain. Furthermore, we show that this information is accessible, even when the system is completely decoupled from the from the normal leads. In this closed regime, we show that the observed quantum capacitance signal is indicative of parity switching between the even and odd ground states. Our measurements in both open and closed regimes confirm that gate reflectometry captures the essential features of interdot coupling and parity dynamics.