Coherent Charge Oscillations in a Bilayer Graphene Double Quantum Dot

TL;DR

This paper reports the first observation of coherent charge oscillations in a bilayer graphene double quantum dot, measuring charge decoherence times and opening avenues for studying charge noise in this promising qubit platform.

Contribution

It demonstrates coherent charge oscillations in bilayer graphene quantum dots and measures charge decoherence times using LZSM interference and photon-assisted tunneling.

Findings

Charge decoherence times are approximately 400-500 ps.

First observation of coherent charge oscillations in bilayer graphene QDs.

Charge noise spectral distribution can be studied in future experiments.

Abstract

The coherent dynamics of a quantum mechanical two-level system passing through an anti-crossing of two energy levels can give rise to Landau-Zener-St\"uckelberg-Majorana (LZSM) interference. LZSM interference spectroscopy has proven to be a fruitful tool to investigate charge noise and charge decoherence in semiconductor quantum dots (QDs). Recently, bilayer graphene has developed as a promising platform to host highly tunable QDs potentially useful for hosting spin and valley qubits. So far, in this system no coherent oscillations have been observed and little is known about charge noise in this material. Here, we report coherent charge oscillations and $T_2^*$ charge decoherence times in a bilayer graphene double QD. The charge decoherence times are measured independently using LZSM interference and photon assisted tunneling. Both techniques yield $T_2^*$ average values in the range of 400 to 500 ps. The observation of charge coherence allows to study the origin and spectral distribution of charge noise in future experiments.