A theoretical preprint reports persistent, state-dependent quantum revivals in a one-dimensional model of interacting Rydberg atoms. In the full model, the starting state |0⟩ produced coherent oscillations, while the alternative state |Z4⟩ did not; the proposed atomic implementation remains untested.
Here, a revival refers to repeated oscillatory returns in the calculated quantum dynamics. The study is based entirely on analytic work and numerical simulations, rather than measurements from an experiment.
A four-site building block
The model is a one-dimensional spin-1/2 chain arranged in four-site units called tetramers. In each unit, the two central atoms can flip together only when both boundary atoms are in the |0⟩ state. When the central pair is excited, its energy also depends on the configuration of all four atoms, creating a constrained four-body interaction.
To study the ground state, the authors used a wavefunction ansatz and reduced the problem to a tridiagonal low-energy Hamiltonian, then compared the analytic result with exact diagonalization, a numerical calculation of the model’s energy levels.
In the thermodynamic-limit analysis, the reported ground-state energy is approximately −0.4148gL, so it scales with the length L of the chain. In a 24-site example, occupation of the inner pairs exceeded 0.5, while occupation at the two ends was below 0.1 and was zero at the edges.
The calculated entanglement entropy—a measure of how strongly two parts of a quantum state are linked—alternated with period 4. It was higher when the cut passed through an inner pair, including at positions 2, 6 and 10.
The pattern at the start matters
The contrast between the two starting states was central to the dynamics. In the model containing only the constrained flip term, |Z4⟩ produced persistent oscillations of central pairs and repeated revivals, while |0⟩ did not show coherent revivals.
The corresponding spectrum contained a high-overlap strip of eigenstates associated with |Z4⟩. The states were spaced by roughly 0.1 in energy, arranged symmetrically around zero, and most had low entanglement entropy. The paper describes this pattern as a quantum many-body scar structure.
Adding the state-dependent four-body term changed which initial pattern retained the organized motion. The full model reported persistent oscillations from |0⟩, including coherent oscillations in bulk dimer stripes, rather than the revivals seen from |Z4⟩ in the kinetic-only case.
The full model’s high-overlap states formed a tower shifted toward |0⟩. The four states with the highest overlap had an average energy spacing of about 0.3, reported as independent of chain length L in the study’s calculations.
The two starting states also differed in their connected long-range correlations. Correlations measured between site 11 and distant sites remained sizable for |0⟩ but decayed rapidly for |Z4⟩.
From equations to atoms
The authors proposed an implementation using alternating Rydberg blockade and antiblockade conditions. The effective description was derived with a Schrieffer–Wolff transformation in the regime Vb ≫ Ω.
The proposal uses 87Rb atoms with alternating spacings of 4 and 8 micrometres and the |76D5/2⟩ Rydberg state. The stated parameters include interactions of approximately 648 MHz and 10.13 MHz, a Rabi frequency divided by 2π of 1 MHz, and a detuning divided by 2π of 5.06 MHz.
Under those stated parameters, the Rydberg simulations showed coherent revivals from |0⟩, and the effective model qualitatively captured the reported non-ergodic dynamics. Keeping only nearest-neighbour interactions left the revivals essentially unchanged in that regime.
A proposal, not a demonstration
The study does not report an experimental realization or measurement of the chain. Its dynamical and scar analysis uses finite chain lengths and selected initial states, so the calculations do not establish the same behavior for every system size or preparation.
The microscopic reduction also relies on rotating-wave, antiblockade, Schrieffer–Wolff and interaction-range approximations. In the derivation presented, the constrained-flip and four-body terms share the same prefactor g and cannot be tuned independently.
The authors identify experimental implementation, independent tuning of the two effective terms and extensions to higher dimensions as open questions. They also suggest testing whether the reported long-range correlations could be useful for quantum sensing, but that possibility was not tested here.
Paper data and sources
Original title: Nonthermal Dynamics of a One-dimensional Rydberg-atom Chain with Constraint Four-body Interactions
Authors: Tianyi Yan, Weibin Li
Journal/Repository: arXiv
Status: Preprint, not yet peer-reviewed
First online: 2026-08-20
DOI: Not available
Original paper · Full text