Finite-size spin fluctuations and fixed-index sweeps in a ferromagnetic spinor condensate
Abstract
We find a dip in the optimized rotation quantum Fisher information of a zero-magnetization ferromagnetic spin-1 Bose-Einstein condensate near the excited-state quantum phase transition. Its displacement from εc=−q decreases on an inverse-size scale. At q=0.6,0.8,1.0,1.2, the dip value of Fmax equals 2⟨ S2⟩ for N up to $3840$, linking it to total-spin fluctuations. A semiclassical orbit average normalized by the classical density of states describes the dip over N=120--$3840$ with maximum relative residual below $0.028$; a small power law fits comparably. Inserting the measured energy offsets directly into the semiclassical formula leaves residuals of $17−−30\%$, so κ acts as an effective cutoff. Among retained states, spin-nematic squeezing occurs at the spectral edges. Separately, fixed-index excited-state sweeps have half-excitation times between $11.2$ and $13.1$ times their ground-state counterparts, with local size exponents increasing across the four sizes.
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BibTeX
@misc{ding2026finitesize,
title = {{Finite-size spin fluctuations and fixed-index sweeps in a ferromagnetic spinor condensate}},
author = {Yi Ding and Junyan Luo and Yixiao Huang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.28163},
eprint = {2610.28163},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.28163},
}
RIS
TY - UNPB
TI - Finite-size spin fluctuations and fixed-index sweeps in a ferromagnetic spinor condensate
AU - Yi Ding
AU - Junyan Luo
AU - Yixiao Huang
PY - 2026
DA - 2026/10/20
PB - arXiv
DO - 10.48550/arxiv.2610.28163
UR - https://arxiv.org/abs/2610.28163
AB - We find a dip in the optimized rotation quantum Fisher information of a zero-magnetization ferromagnetic spin-1 Bose-Einstein condensate near the excited-state quantum phase transition. Its displacement from ε_c=−q decreases on an inverse-size scale. At q=0.6,0.8,1.0,1.2, the dip value of F_max equals 2⟨ S^2⟩ for N up to $3840$, linking it to total-spin fluctuations. A semiclassical orbit average normalized by the classical density of states describes the dip over N=120--$3840$ with maximum relative residual below $0.028$; a small power law fits comparably. Inserting the measured energy offsets directly into the semiclassical formula leaves residuals of $17−−30\%$, so κ acts as an effective cutoff. Among retained states, spin-nematic squeezing occurs at the spectral edges. Separately, fixed-index excited-state sweeps have half-excitation times between $11.2$ and $13.1$ times their ground-state counterparts, with local size exponents increasing across the four sizes.
ER -