Enhanced charge detection of spin qubit readout via an intermediate state

TL;DR

This paper introduces a method using an intermediate charge state in a quantum dot to enhance charge detection contrast, significantly improving the visibility of qubit oscillations without increasing detector noise.

Contribution

The novel approach employs an intermediate excited charge state to amplify qubit oscillation signals, boosting readout contrast in spin qubit measurements.

Findings

Enhanced fringe contrast of Landau-Zener-Stückelberg oscillations

Increased signal-to-noise ratio in charge detection

Demonstrated improved qubit state readout fidelity

Abstract

We employ an intermediate excited charge state of a lateral quantum dot device to increase the charge detection contrast during the qubit state readout procedure, allowing us to increase the visibility of coherent qubit oscillations. This approach amplifies the coherent oscillation magnitude but has no effect on the detector noise resulting in an increase in the signal to noise ratio. In this letter we apply this scheme to demonstrate a significant enhancement of the fringe contrast of coherent Landau-Zener-Stuckleberg oscillations between singlet S and triplet T+ two-spin states.