# Rapid detection of coherent tunneling in an InAs nanowire quantum dot through dispersive gate sensing

## TL;DR

This paper demonstrates rapid, high-fidelity detection of coherent electron tunneling in InAs nanowire quantum dots using dispersive gate sensing, enabling potential applications in topological qubit readout.

## Contribution

The authors developed a sensitive dispersive detection circuit that measures single-electron tunneling amplitudes on microsecond timescales in a quantum dot system.

## Key findings

- Achieved a dispersive shift comparable to the resonator linewidth at charge degeneracy.
- Differentiated Coulomb blockade from resonance with high signal-to-noise ratio.
- Enabled potential for single-shot fermion parity measurements in topological qubits.

## Abstract

Dispersive sensing is a powerful technique that enables scalable and high-fidelity readout of solid-state quantum bits. In particular, gate-based dispersive sensing has been proposed as the readout mechanism for future topological qubits, which can be measured by single electrons tunneling through zero-energy modes. The development of such a readout requires resolving the coherent charge tunneling amplitude from a quantum dot in a Majorana-zero-mode host system faithfully on short time scales. Here, we demonstrate rapid single-shot detection of a coherent single-electron tunneling amplitude between InAs nanowire quantum dots. We have realized a sensitive dispersive detection circuit by connecting a sub-GHz, lumped element microwave resonator to a high-lever arm gate on one of dots. The resulting large dot-resonator coupling leads to an observed dispersive shift that is of the order of the resonator linewidth at charge degeneracy. This shift enables us to differentiate between Coulomb blockade and resonance, corresponding to the scenarios expected for qubit state readout, with a signal to noise ratio exceeding 2 for an integration time of 1 microsecond. Our result paves the way for single shot measurements of fermion parity on microsecond timescales in topological qubits.