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arXiv:2606.00242

Experimental observation of strong field stabilization

Anna R. Dardia, Spencer Walker, Yifei Bai, Petros Kousis, Alexandra S. Landsman, David Weld

Published May 29, 2026• 0 citations
arXivHTMLPDF

Abstract

Bound quantum states such as atoms can be torn apart by strong oscillating fields. A natural expectation is that stronger fields lead to more certain destruction. In contradiction to this intuition, some theories predict a striking reversal: that as the field intensity is raised above some threshold, bound state wavefunctions can spatially bifurcate and become increasingly stable with increasing field intensity. This ``strong field stabilization'' was predicted decades ago in the context of atoms in pulsed laser fields, but has resisted experimental observation due to extreme laser intensity requirements and theoretical controversy. We report the experimental observation of strong-field stabilization of a ground state, using trapped neutral atoms to emulate the dynamics of atomic electrons in an extremely strong laser field. We directly image the predicted wavepacket bifurcation, measure an ionization rate non-monotonic in field amplitude, and map out the regime of stabilization as a function of laser pulse parameters. We observe that stabilization persists down to surprisingly low drive frequencies, near and below the scale of the lowest-energy excitations of the bound state. These results confirm and extend a long-standing prediction of extreme quantum dynamics, and showcase a complementary tool for probing strong-field phenomena near and beyond the frontier of current laser technology.

DOI
10.48550/arxiv.2606.00242

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Stabilizing atoms exposed to intense laser fields has been a central topic in atomic physics for decades, inspiring several theoretical frameworks that describe the phenomenon under different resonance conditions and coupling regimes. Here, we theoretically investigate an ionizing electronic transition driven by a resonant pump field, in contrast to Kramers–Henneberger atoms, which are stabilized by non-perturbative, non-resonant laser pulses. We show that, above a critical pump intensity, the drive creates a metastable electronic bound state emerging from the continuum, which decays via two-photon ionization. We calculate the resulting resonant fluorescence spectrum and find a qualitatively different structure from the familiar Mollow triplet associated with bound-to-bound transitions. This fluorescence provides a time-resolved probe of the population in the metastable state. In analogy to how the AC Stark shift is a semiclassical counterpart of the single-photon Rabi splitting observed in optical cavities, the phenomenon we describe is best understood as a semiclassical analog of recently observed excitons bound by a single cavity photon.
Abstract Ultrafast electronic dynamics are typically studied using pulsed lasers. Here we demonstrate a complementary experimental approach: quantum simulation of ultrafast dynamics using trapped ultracold atoms. Counter-intuitively, this technique emulates some of the fastest processes in atomic physics with some of the slowest, leading to a temporal magnification factor of up to 12 orders of magnitude. In these experiments, time-varying forces on neutral atoms in the ground state of a tunable optical trap emulate the electric fields of a pulsed laser acting on bound charged particles. We demonstrate the correspondence with ultrafast science by a sequence of experiments: nonlinear spectroscopy of a many-body bound state, control of the excitation spectrum by potential shaping, observation of sub-cycle unbinding dynamics during strong few-cycle pulses, and direct measurement of carrier-envelope phase dependence of the response to an ultrafast-equivalent pulse. These results establish cold-atom quantum simulation as a complementary tool for studying ultrafast dynamics.
We demonstrate a physical quantum simulator of ultrafast phenomena, in which time-varying forces on neutral atoms in a tunable optical trap emulate the electric fields of a pulsed laser acting on electrons or nuclei in a binding potential. The simulator operates in regimes equivalent to those of ultrafast and strong-field pulsed-laser experiments, opening up a hitherto unexplored application of quantum simulation techniques and a complementary path towards investigating open questions in ultrafast science. Counter-intuitively, this approach emulates some of the fastest processes in atomic physics with some of the slowest, giving rise to a temporal magnification factor of up to twelve orders of magnitude which greatly simplifies experimental access to the dynamics. The correspondence with ultrafast science is demonstrated by a sequence of experiments: we perform nonlinear spectroscopy of a many-body bound state, control the excitation spectrum by shaping the potential, observe sub-cycle unbinding dynamics during strong few-cycle pulses, and directly measure carrier-envelope phase dependence of the response to an ultrafast-equivalent pulse.
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