Readout Of Singlet-Triplet Qubits At Large Magnetic Field Gradients

TL;DR

This paper introduces a robust readout method for singlet-triplet qubits that remains effective under large magnetic field gradients by mapping qubit states onto relaxation-immune spin states, enhancing measurement reliability.

Contribution

The authors develop and experimentally validate a new singlet-triplet qubit readout technique that is resilient to relaxation effects caused by large magnetic field gradients.

Findings

Readout visibility remains high at large magnetic field gradients.

The new method outperforms previous techniques in relaxation environments.

Optimized pulse sequences improve measurement fidelity.

Abstract

Visibility of singlet-triplet qubit readout is reduced to almost zero in large magnetic field gradients due to relaxation processes. Here we present a new readout technique that is robust against relaxation and allows for measurement when previously studied methods fail. This technique maps the qubit onto spin states that are immune to relaxation using a spin dependent electron tunneling process between the qubit and the lead. We probe this readout's performance as a function of magnetic field gradient and applied magnetic field, and optimize the pulse applied to the qubit through experiment and simulation.