Tuning Boron-Vacancy Qubit Coherence through Layer Number in hBN
Abstract
The negatively charged boron vacancy (VB) in hexagonal boron nitride (\hBN{}) was the first optically addressable spin qubit identified inside a van der Waals crystal, allowing atomically defined placement relative to a target. Its coherence in bulk \hBN{} is limited by the boron nuclei of the layers flanking the defect plane, which a thin flake removes. Here, we use a generalized cluster-correlation expansion with an extended central-spin block to calculate the Hahn-echo coherence time of VB in h11B15N as a function of layer number. Our results show that T2 rises from 199ns in the bulk limit to 653ns in a monolayer, a factor of $3.3$ that is already saturated at three layers and that a sublattice decomposition attributes entirely to boron. The enhancement is confined to low field, is insensitive to stacking registry and twist angle, and requires alignment to within about two degrees, an onset we reproduce with no free parameters. Under dynamical decoupling, a 1/e threshold returns 206ns for every thickness, but this is a zero of the first-shell modulation rather than a decay: measured without a threshold, the layer contrast survives and reaches a factor of $170$. Layer number thus emerges as a design parameter for VB-based sensing.
Related
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BibTeX
@misc{florez2026tuning,
title = {{Tuning Boron-Vacancy Qubit Coherence through Layer Number in hBN}},
author = {Juan M. Florez and Eric Suárez Morell},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.01812},
eprint = {2609.01812},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.01812},
}
RIS
TY - UNPB
TI - Tuning Boron-Vacancy Qubit Coherence through Layer Number in hBN
AU - Juan M. Florez
AU - Eric Suárez Morell
PY - 2026
DA - 2026/09/01
PB - arXiv
DO - 10.48550/arxiv.2609.01812
UR - https://arxiv.org/abs/2609.01812
AB - The negatively charged boron vacancy (VB) in hexagonal boron nitride (\hBN{}) was the first optically addressable spin qubit identified inside a van der Waals crystal, allowing atomically defined placement relative to a target. Its coherence in bulk \hBN{} is limited by the boron nuclei of the layers flanking the defect plane, which a thin flake removes. Here, we use a generalized cluster-correlation expansion with an extended central-spin block to calculate the Hahn-echo coherence time of VB in h^11B^15N as a function of layer number. Our results show that T_2 rises from 199ns in the bulk limit to 653ns in a monolayer, a factor of $3.3$ that is already saturated at three layers and that a sublattice decomposition attributes entirely to boron. The enhancement is confined to low field, is insensitive to stacking registry and twist angle, and requires alignment to within about two degrees, an onset we reproduce with no free parameters. Under dynamical decoupling, a 1/e threshold returns 206ns for every thickness, but this is a zero of the first-shell modulation rather than a decay: measured without a threshold, the layer contrast survives and reaches a factor of $170$. Layer number thus emerges as a design parameter for VB-based sensing.
ER -