A Surface-Scaffolded Molecular Qubit

TL;DR

This paper introduces a surface-supported molecular qubit using pentacene on hBN, demonstrating long coherence times and surface integration, advancing quantum sensing and hybrid quantum device development.

Contribution

The work presents a novel surface molecular qubit with long coherence times, scalable fabrication, and compatibility with 2D materials, outperforming existing shallow NV centers.

Findings

Hahn-echo coherence reaches 22 μs with deuterated pentacene.

Coherence extends to 214 μs under dynamical decoupling.

The platform enables mapping local spin environments.

Abstract

Fluorescent spin qubits are central building blocks of quantum technologies. Placing these qubits at surfaces maximizes coupling to nearby spins and fields, enabling nanoscale sensing and facilitating integration with photonic and superconducting devices. However, reducing the dimensions or size of established qubit systems without sacrificing the qubit performance or degrading the coherence lifetime remains challenging. Here, we introduce a surface molecular qubit formed by pentacene molecules scaffolded on a two-dimensional (2D) material, hexagonal boron nitride (hBN). The qubit exhibits stable fluorescence and optically detected magnetic resonance (ODMR) from cryogenic to ambient conditions. With fully deuterated pentacene, the Hahn-echo coherence reaches 22 $\mu$s and further extends to 214 $\mu$s under dynamical decoupling, outperforming state-of-the-art shallow NV centers in diamond, despite being positioned directly on the surface. We map the local spin environment, resolving couplings to nearby nuclear and electron spins that can serve as auxiliary quantum resources. This platform combines true surface integration, long qubit coherence, and scalable fabrication, opening routes to quantum sensing, quantum simulation, and hybrid quantum devices. It also paves the way for a broader family of 2D material-supported molecular qubits.