Spin defects in aqueous environments

Spin defects in two-dimensional (2D) materials are promising platforms for quantum information technologies: compared with thin films of 3D solids, 2D systems are usually free from unsaturated surface dangling bonds, which are detrimental to spin coherence [1]. In this work, we investigate spin defects in 2D materials as sensors in aqueous environments, by exploring the effect of the magnetic field induced by the protons of liquid water, specifically the effect of protons on the coherence T₂ of the qubit. We discuss how motional narrowing, a well-known phenomenon in classical Nuclear Magnetic Resonance (NMR), arises and affects the defect coherence time. We consider an NV-like spin defect in graphene and a negatively charged boron-vacancy in h-BN, and we present results as a function of temperature, confinement distance between the 2D layers, surface hydrophobicity and ion concentration in proximity of the surface. We first generate a structural model of the 2D/water interface by performing classical Molecular Dynamics (MD) simulations using the LAMMPS code [2], and then we use our trajectories to generate spin bath configurations and compute coherence properties using the PyCCE code [3].

[1] Ye et al. npj Comput Mater, 2019.

[2] Thompson et al. Comp Phys Comm, 2022.

[3] Onizhuk et al. Adv Theory Simul, 2021