Loop-Dressed LLB Dynamics: Non-Equilibrium Phenomena and Entanglement in the Jeener 8-Spin Cube

Dipolar coupled spin systems display rich non-equilibrium phenomena ranging from spectral clustering to turbulence. Jeener's 8-spin cube model has served as a minimal, reproducible geometry to probe these effects with classical spin equations. We revisit the Jeener cube with a loop-dressed Landau–Lifshitz–Bloch (LLB) model that adds a quantum fluctuation field N derived from a Keldysh rotation to the classical magnetization M. This model captures fluctuation–dissipation, short-memory kernels, and loop corrections in mesoscopic spin packets. We report results up to 4 loop orders and analyze the effect of different loop parameters and noise on the dynamics. We also report pairwise qubit entanglement and Gaussian (CV) entanglement measures, identifying regimes potentially promising for collective-spin Berry-phase quantum computing.