Probing false vacuum decay and bubble nucleation in a Rydberg atom array

TL;DR

The study uses a programmable Rydberg-atom ring to simulate FV decay and bubble nucleation in a generalized Ising model with long-range interactions and a staggered longitudinal field. By preparing a proper metastable PQG state and tuning the symmetry-breaking field, the authors observe an exponential suppression of the FV-decay rate with inverse field strength, in line with instanton-based predictions, while a Néel initial state shows deviations due to fluctuations. They demonstrate that PQG dynamics obey the universal exponential scaling across extended parameter ranges and model the short-time behavior with a Baker–Campbell–Hausdorff expansion to reveal symmetry-imposed structure, including vanishing odd orders. In the long-time regime, they access resonant bubble nucleation under a ramp protocol, revealing discrete-spectrum–driven dynamics and outlining a path toward studying many-body tunneling in more complex geometries and higher dimensions.

Abstract

In quantum field theory (QFT), the "vacuum" is not just empty space but the lowest-energy state of a quantum field. If the energy landscape has multiple local minima, the local ground states are the false vacuum (FV) which can tunnel towards the global ground state (true vacuum, TV). This process exhibits signature akin to classical supercooled gas transitions and many-body tunneling in discrete quantum systems. Here, we study the FV decay and bubble nucleation in a Rydberg atom ring. The long-range van-der-Waals interactions and individual-site addressability allow us to explore physics beyond the standard Ising model. We observe that the FV decay rate decreases exponentially with the inverse of the symmetry-breaking field, directly mirroring QFT predictions. Moreover, we demonstrate that even minor deviations from the ideal metastable state can cause a stark departure from this universal scaling law. Extending beyond short-time decay dynamics, we also examine resonant bubble nucleation, a feature distinctive to systems with discrete energy spectra. Our findings and methods open avenues for future studies of many-body tunneling in higher dimensions or more complex geometries.

Figures (10)

• Figure 1: Simulating false vacuum decay with a programmable Rydberg atom array. (a) Schematic of the experimental setup. Neutral atoms are trapped in a ring geometry and illuminated globally by the 420-nm and 1013-nm lasers, coupling the ground state to a high-lying Rydberg state (70S). A set of far-detuned, site-selective addressing lasers (pink beams) illuminates every other atom, generating a staggered detuning. A magnetic field $B$ parallel to the 420-nm laser defines the quantization axis. (b) Energy landscape for false vacuum decay in an antiferromagnetic Ising model. The staggered longitudinal field breaks the degeneracy of the two Néel-ordered ground states, creating a metastable false vacuum and a stable true vacuum. Quantum tunneling from the false vacuum towards the true vacuum proceeds via the nucleation of true vacuum bubbles (illustrated as gray domains of flipped spins). The dashed lines denote static energies ($\Omega=0$) of representative spin configurations along the unfolded ring.
• Figure 2: Dynamics and scaling of the false vacuum decay. Main panel: Measured time evolution of the rescaled antiferromagnetic (AFM) order for an $N=16$ atom ring, plotted on a logarithmic scale for different $V/\Delta_l$ ratios. Experimental data (solid squares) are averaged over 300 realizations. Solid lines are exponential fits $M_{\text{AFM}}^{\text{~res}}(t) \propto e^{-\gamma t}$ to the data within time windows $t \in [0.02,0.18]~\rm{\mu}s$, used to extract the decay rate $\gamma$. Dashed lines are extensions of these fits. Inset: Extracted decay rate $\gamma$, normalized by $\Omega$, as a function of the inverse local staggered field $V/\Delta_l$. Experimental results for $N=16$ (empty diamonds) and $N=24$ (solid hexagons) are shown with statistical error bars. The gray line is the decay rate extracted from numerical simulations for $N=16$ without considering any experimental errors.
• Figure 3: Comparison of FV decay of an initial Néel state (blue squares) versus the pre-quench ground (PQG) state (orange pentagons). (a) Measured evolution of the AFM order starting from the Néel state versus PQG state, for $\Delta_l/V=0$ (left) and $\Delta_l/V=0.08$ (right). Solid lines connecting data points are guides to the eye. Dashed lines are numerical simulations that include decoherence at the bench-marked level. (b) Comparison of decay rates, extracted from numerical simulation, for the Néel and PQG states as a function of $V/\Delta_l$. The left panel shows the result for $\Delta_g/V=1$, and the solid gray line is the theoretical prediction based on Eq. (6) of Ref. 2021_Lagnese_FVDinSpinChains without any fitting parameters. The right panel shows the result for $\Delta_g/V=0.8$, and the dashed gray line represents a linear fit for the PQG data.
• Figure 4: Resonant nucleation of true-vacuum bubbles. (a) Energy landscape of the product states (in grey filled circles) at the $L=2$ resonance ($V/\Delta_l \approx 2$) forming a nearly triangular grid, on which the final state projection is drawn according to the color bar. Starting from the Néel state (lower left), the final state preferentially populating the $L=2$ bubble manifolds, with the most probable four-bubble manifold illustrated at the lower right. (b) Measured bubble density for sizes $L=1, 2, 3$ during the ramp (at $V/\Delta_l=2$), showing the steepest increase for the $L=2$ bubbles. (c-e) Experimental verification of the resonance condition. The final bubble densities $\langle\Sigma_L\rangle$ are plotted versus $V/\Delta_l$ for $L=1$ (c), $L=2$ (d), and $L=3$ (e), revealing distinct peaks at their respective $V/\Delta_l \approx L$. Ramp parameters ($\Omega_f/(2\pi), T$) are independently optimized for each $L$ to maximize the signal: (c) ($1$ MHz, $0.5~\mu$s); (d) ($1.8$ MHz, $1~\mu$s); (e) ($1.8$ MHz, $2~\mu$s).
• Figure S1: Experimental time sequence for Néel state preparation and subsequent decay measurement. The sequence consists of adiabatic transfer, Néel state preparation via a Landau-Zener sweep, the decay process under the target Hamiltonian, and the final projective measurement.