Fast high-fidelity baseband reset of a latched state for quantum dot qubit readout

TL;DR

This paper introduces a rapid, high-fidelity method to reset a quantum dot qubit from a latched charge state using a single voltage pulse, significantly improving readout speed and fidelity.

Contribution

It presents a simple, on-demand reset technique for quantum dot qubits that drastically reduces reset time while maintaining over 99% fidelity.

Findings

Reset time is reduced by over 50 times compared to passive methods.

Achieved reset fidelity exceeds 99%.

Optimal reset region identified in the qubit gate voltage space.

Abstract

A common method for reading out the state of a spin qubit is by latching one logical qubit state, either $|1\rangle$ or $|0\rangle$, onto a different, metastable charge state. Such a latched state can provide a superior charge sensing signal for qubit readout, and it can have a lifetime chosen to be long enough that the charge sensed readout can be high fidelity. However, the passive reset out of latched states is inherently long, which is not desirable. In this work, we demonstrate an on-demand, high fidelity (> 99%) re-initialization of a quantum dot qubit out of a latched readout state. The method is simple to apply as it involves a single baseband voltage pulse to a specific region in the quantum dot stability diagram where the relaxation time from the latched state to the ground state is over 50 times faster. We describe the mechanism for the reset process as well as the boundaries for the optimal reset region in the qubit gate voltage space.