Electrostatically defined quantum dots in bilayer graphene offer a promising platform for spin qubits with presumably long coherence times due to low spin-orbit coupling and low nuclear spin density. We demonstrate two different experimental approaches to measure the decay times of excited states. The first is based on direct current measurements through the quantum device. Pulse sequences are applied to control the occupation of ground and excited states. We observe a lower bound for the excited state decay on the order of hundred microseconds. The second approach employs a capacitively coupled charge sensor to study the time dynamics of the excited state using the Elzerman technique. We find that the relaxation time of the excited state is of the order of milliseconds. We perform single-shot readout of our two-level system with a visibility of 87.1%, which is an important step for developing a quantum information processor in graphene.
Cite
@article{arxiv.2112.12091,
title = {Single-shot readout in graphene quantum dots},
author = {Lisa Maria Gächter and Rebekka Garreis and Chuyao Tong and Max Josef Ruckriegel and Benedikt Kratochwil and Folkert Kornelis de Vries and Annika Kurzmann and Kenji Watanabe and Takashi Taniguchi and Thomas Ihn and Klaus Ensslin and Wister Wei Huang},
journal= {arXiv preprint arXiv:2112.12091},
year = {2022}
}