Parity-doublet spin interactions in ultracold polyatomic molecules
Abstract
Precision measurements exploit internal molecular structure to search for physics beyond the Standard Model. Reaching the entanglement-enhanced regime requires preparing and preserving correlated molecular states within the same manifold used for sensing. Parity-doublet states are central to proposals for precision measurements with polyatomic molecules because they enable large molecular polarization for enhanced sensitivity, and provide internal state co-magnetometry to suppress systematic errors. Here we report the observation and control of resonant dipolar exchange interactions in a parity-doublet sensing manifold of ultracold polyatomic molecules. Using laser-cooled CaOH molecules in a crossed optical dipole trap, we encode a pseudospin in the ℓ-type parity-doublet states and observe two complementary signatures of interactions: a density-dependent Ramsey contrast decay and a spin-projection-dependent mean-field precession whose sign reverses with the initialized population imbalance. Both observables are well described by a common discrete truncated Wigner model using independently calibrated experimental parameters. We further Floquet-engineer the interaction anisotropy and observe suppressed many-body dephasing near the SU(2)-symmetric Heisenberg point, identifying a protected regime relevant for spin squeezing and precision measurement with dense molecular ensembles. Our results establish parity doublets as a coherent, interacting, and programmable molecular degree of freedom, connecting the polyatomic precision-measurement platform to dipolar many-body physics and opening a route to entanglement-enhanced tests of fundamental physics.
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BibTeX
@misc{tao2026paritydoublet,
title = {{Parity-doublet spin interactions in ultracold polyatomic molecules}},
author = {Junheng Tao and Paige Robichaud and Christian Hallas and Giseok Lee and John M. Doyle},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.36061},
eprint = {2610.36061},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.36061},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Parity-doublet spin interactions in ultracold polyatomic molecules
AU - Junheng Tao
AU - Paige Robichaud
AU - Christian Hallas
AU - Giseok Lee
AU - John M. Doyle
PY - 2026
DA - 2026/10/26
PB - arXiv
DO - 10.48550/arxiv.2610.36061
UR - https://arxiv.org/abs/2610.36061
AB - Precision measurements exploit internal molecular structure to search for physics beyond the Standard Model. Reaching the entanglement-enhanced regime requires preparing and preserving correlated molecular states within the same manifold used for sensing. Parity-doublet states are central to proposals for precision measurements with polyatomic molecules because they enable large molecular polarization for enhanced sensitivity, and provide internal state co-magnetometry to suppress systematic errors. Here we report the observation and control of resonant dipolar exchange interactions in a parity-doublet sensing manifold of ultracold polyatomic molecules. Using laser-cooled CaOH molecules in a crossed optical dipole trap, we encode a pseudospin in the ℓ-type parity-doublet states and observe two complementary signatures of interactions: a density-dependent Ramsey contrast decay and a spin-projection-dependent mean-field precession whose sign reverses with the initialized population imbalance. Both observables are well described by a common discrete truncated Wigner model using independently calibrated experimental parameters. We further Floquet-engineer the interaction anisotropy and observe suppressed many-body dephasing near the SU(2)-symmetric Heisenberg point, identifying a protected regime relevant for spin squeezing and precision measurement with dense molecular ensembles. Our results establish parity doublets as a coherent, interacting, and programmable molecular degree of freedom, connecting the polyatomic precision-measurement platform to dipolar many-body physics and opening a route to entanglement-enhanced tests of fundamental physics.
ER -