We experimentally investigate trapped ion dynamics in the strong-driving regime, where the Rabi frequency $\mathrm{\Omega }$ is comparable to the vibrational mode frequency $\nu$. In the conventional weak-driving regime ($\mathrm{\Omega }\ll \nu$), the dynamics is well described by effective Hamiltonians for the carrier and motional sidebands, associated with detunings $\delta =n\nu$ ($n=0,\pm 1,...$). In the strong-driving regime ($\mathrm{\Omega }\sim \nu$), these interactions can no longer be treated independently. We characterize this physics through the reduced dynamics of the qubit, where non-Markovian behavior emerges as an operational probe of the spin-motion coupling. We observe a structured non-Markovian response, with well-defined maxima that follow the generalized resonance condition ${\delta }^2+{\mathrm{\Omega }}^2={\nu }^2$, reflecting the strong underlying spin-motion hybridization characteristic of the strong-driving regime.

Recent advancements in topological analysis offer a powerful way to classify how phases of nonlinear bosonic resonators organize. These tools are rooted in the Morse-Smale flow topology framework, where a graph-based construction describes how steady-state solutions are arranged in phase space. This construction remains incomplete as self-sustained oscillations in the form of limit cycles can impact the global connectivity of phase-space flows and the corresponding Morse-Smale topological classification. In this work, we extend the bosonic classification scheme to include limit cycles as fundamental topological elements. We illustrate the approach with a minimal nonlinear Van der Pol resonator model, where limit cycles coexist with steady-state solutions. Our results provide a unified topological description of stationary and time-periodic phases in nonlinear bosonic systems, with direct relevance to photonic, superconducting, and optomechanical platforms. Our findings raise fundamental questions regarding synchronization and the extension of flow topology to the quantum regime.

FeGe is the only known kagome metal hosting the coexistence of long-range magnetic order and charge-density-wave (CDW) order, making it an exceptional platform for studying spin-charge-lattice entanglement. Despite extensive experimental and theoretical efforts, the microscopic origin of the CDW in FeGe remains under active debate. In this work, we reveal how in-plane tensile strain reshapes the hierarchy of competing CDW orders in the antiferromagnetic kagome metal FeGe. First-principles phonon calculations uncover two Kohn-anomaly-induced incommensurate CDWs under strain, while slight electron correlations suppress these modes and instead lead to unconventional correlation-driven CDW phases. Notably, a previously unreported fully dimerized $\sqrt{3}\times \sqrt{3}\times 2$ CDW emerges from the softened H-point phonon mode. Total-energy analyses establish a strain-induced phase transition sequence: $2\times 2\times 2\to \sqrt{3}\times \sqrt{3}\times 2\to$ fully dimerized $\sqrt{3}\times \sqrt{3}\times 2$ at strains of $\sim 0.6\%$ and $\sim 2.4\%$, respectively, while a small U = 0.2 eV will reduce the required strain to $\sim 0.2\%$ and $\sim 1.8\%$, respectively. These results demonstrate the coexistence of electron-phonon-driven and correlation-driven CDW mechanisms, positioning strained FeGe as a powerful platform for probing strongly coupled spin-charge-lattice entanglement in correlated magnetic kagome systems.

Much attention has been devoted to the use of machine learning to approximate physical concepts. Yet, due to challenges in interpretability of machine learning techniques, the question of what physics machine learning models are able to learn remains open. Here, we bridge the concept of a physical quantity and its machine learning approximation in the context of the original application of neural networks in physics: topological phase classification. We construct a hybrid tensor-neural network object that exactly expresses the real-space topological invariant and rigorously assess its trainability and generalization. Specifically, we benchmark the accuracy and trainability of a tensor-neural network to multiple types of neural networks, thus exemplifying the differences in trainability and representational power. Our work highlights the challenges in learning topological invariants and constitutes a stepping stone toward more accurate and better generalizable machine learning representations in condensed matter physics.

We introduce and theoretically analyze a quantum interference phenomenon in which a two-photon interference pattern is created using four-photon quantum states generated by two independent sources and without detecting two of the photons. Contrary to the common perception, the interference pattern can be made fully independent of phases acquired by the photons detected to construct it. However, it still contains information about spatially dependent phases acquired by the two undetected photons. This phenomenon can be observed with both bosonic and fermionic particles. We show that the phenomenon can be harnessed to develop a quantum quantitative phase imaging technique that is immune to uncontrollable phase fluctuations in the interferometer and allows image acquisition without detecting the photons illuminating the object.

Plants navigate fluctuating fluid environments in both soil and hydroponic systems, yet the physical principles by which roots transduce directional hydrodynamic forcing into developmental responses remain poorly quantified. By combining a flow-configurable microfluidic platform (P-ROOT) with fluid-structure interaction modeling and multiscale phenotyping, we establish a dimensionless, direction-dependent hydraulic stress index, defined as the ratio of flow-induced stress to root stiffness, that predicts growth-permissive and stress-adaptive hydraulic loading regimes in Brassica juncea roots. Our results reveal a pronounced directional asymmetry: Under parallel flow, root elongation is sustained across a broad hydraulic loading range, whereas counterflow concentrates stress near the root apex, restricting the growth-permissive range and reducing elongation. Transitions across these hydraulic loading regimes coincide with coordinated cortical remodeling, auxin redistribution, reduced nitrogen uptake, and enhanced nitro-oxidative signatures near the root tip. These findings indicate that root developmental plasticity is governed more strongly by localized stress amplification than by the overall magnitude of hydraulic loading. By establishing hydraulic stress indices as predictive metrics linking mechanical loading to multiscale biological responses, this work provides a quantitative framework for understanding plant-fluid interactions and for designing flow-managed cultivation systems that optimize nutrient delivery.

We introduce the concept of quantum observables over time (QOOT), an operator that jointly describes two observables at two distinct time points, as a dual of the quantum state over time formalism. We provide a full characterization of the conditions under which a QOOT can be properly defined, via a no-go theorem. We use QOOTs to establish a notion of time reversal for generic quantum channels with respect to a reference observable, enabling the systematic construction of recovery maps that preserve the latter. These recovery maps, although generally nonphysical, can be decomposed into realizable channels, enabling their application in noiseless expectation value estimation tasks. We provide explicit examples and compare our protocol with other error mitigation methods. We show that our protocol retrieves the noiseless expectation value of the reference observable and can achieve optimal sampling overhead, outperforming probabilistic error cancellation.

Molecular nanomagnets are compounds characterized by a high-spin magnetic core that is protected by organic ligands. They have recently gained attention as potential quantum information carriers in solid-state quantum computing platforms, simultaneously exhibiting classical macroscopic properties and quantum features in light of their complex nature and configuration. Addressing the condition when they manifest unquestionable quantum behavior is key to guarantee their effectiveness as resources for quantum information processing. We address the quantumness of molecular nanomagnets using a recently formulated criterion [T. Krisnanda et al., Phys. Rev. Lett. 119, 120402 (2017)] demonstrating that these systems exhibit an intrinsic quantum nature, as evidenced by their ability to generate and enhance quantum correlations between two noninteracting probes. Our analysis, which is performed addressing various dynamical regimes, paves the way to the design of experimentally viable tests of nonclassicality in multipartite registers consisting of ensembles of molecular nanomagnets.

We investigate the nature of the excitations captured by the dynamical response of XYZ triangular spin-1/2 ladders. We complement experimental inelastic neutron scattering results on the compound ${\mathrm{Cs}}_2{\mathrm{CoBr}}_4$ with numerically exact simulations based on time-dependent matrix product state methods. Our results show that bound states of spinon excitations can arise in XYZ beyond the requirement of strong Ising anisotropies. We analyze the role of the frustrated triangular couplings on the excitations giving rise to the spin dynamical structure factor and show how the features of the bound states manifest themselves in the different polarization channels.

Intermittency represents a fundamental route to chaos in nonlinear dynamical systems. In this work, we introduce an adaptive control strategy in which the control parameter of an intermittent system is promoted to a dynamical variable that evolves autonomously under an auxiliary nonlinear map drawn from the same functional hierarchy as the system itself. The construction eliminates the need for orbit identification, local linearization, and trajectory-triggered perturbations, which are central ingredients of conventional feedback schemes. The theoretical framework is developed within a class of one-dimensional nonlinear ergodic maps with exactly known invariant (Sinai-Ruelle-Bowen) measures, for which we derive in closed form (1) the dynamics and invariant measure of the evolving control parameter, (2) the invariant measure of the coupled system, and (3) the $q$-generalized Lyapunov exponents before and after control. The generalized Lyapunov spectrum serves as an analytical order parameter for the control process: The collapse of its positive regions provides a quantitative and initial-condition-independent signature of chaos suppression, and yields the sensitivity to initial conditions in explicit form. To establish the physical relevance of the approach beyond low-dimensional maps, we apply the same construction to a cluster of three interacting ultrasound-driven microbubbles described by the Keller-Herring model, promoting the experimentally accessible acoustic driving frequency to a dynamical variable. Systematic bifurcation and Lyapunov analyses, performed over wide ranges of driving pressure, frequency, and equilibrium radii, demonstrate that intermittent chaotic radial oscillations are progressively suppressed and replaced by stable periodic motion. These results establish intermittency regulation as a unifying and physically realizable mechanism for stabilizing complex nonlinear dynamics.

Recent experiments with rotating Bose gases have demonstrated the interaction-driven hydrodynamic instability of an initial extended striplike state in the lowest Landau level. We investigate this phenomenon in the low-density limit, where the mean-field Gross-Pitaevskii theory becomes inadequate, using exact diagonalization studies and analytic arguments. We show that the behavior can be understood in terms of weakly interacting repulsively bound few-body clusters. Signatures of cluster behavior are observed in the expectation values of observables that oscillate at frequencies characterized by the energies of few-body bound states. Using a semiclassical theory for interacting clusters, we predict the long-time growth of the cloud width to be a power law in the logarithm of time. This slow thermalization of bound clusters represents a form of quantum many-body scars.

Variational quantum algorithms (VQAs) aim at solving classical or quantum optimization problems by optimizing parametrized trial states on a quantum device, based on the outcomes of noisy projective measurements. The associated optimization process benefits from an accurate modeling of the cost function landscape using Gaussian process models (GPMs), whose performance is critically affected by the choice of their kernel. Here, we introduce specialized trigonometric kernels, inspired by the observation that typical VQA cost functions display oscillatory behavior with only few frequencies. Appropriate scores to benchmark the reliability of a GPM are defined, and a systematic comparison between different kernels is carried out on prototypical problems from quantum chemistry and combinatorial optimization. We further introduce RotoGP, a sequential line-search optimizer equipped with a GPM, and test how different kernels can help mitigate noise and improve optimization convergence. Overall, we observe that the trigonometric kernels show the best performance in most of the cases under study.

Schelling's model of segregation demonstrates that even in the absence of social or governmental interventions, individuals with mild in-group preferences can self-organize into strongly segregated neighborhoods. Many variants of this celebrated model have been proposed by assuming that agents tend to increase their satisfaction. Complementary to this traditional, utility-based approach, we model residential moves using satisfaction-independent reaction rates in a spatially extended chemical reaction network. The resulting model exhibits an emergent phenomenon: Despite symmetric in-group preferences, the system undergoes a tipping transition at a critical preference level, beyond which one agent type dominates. We characterize this asymmetric phase transition in details using mean-field analysis, numerical simulations, and finite-size-scaling methods. We find that while the transition shares key features with the Ising-universality class, such as ${\mathbb{Z}}_2$ symmetry breaking and similar exponent ratios, the full set of critical exponents does not match any known universality class.

We investigate collective search by self-propelled agents that are repelled by their own chemically produced trails, a minimal mechanism that simultaneously generates indirect interactions and memory. Using lattice and off-lattice models, we show that this mechanism enhances search efficiency through two distinct regimes. In a weak-memory regime, chemical cues are short-lived and interactions primarily promote spatial separation between agents. This reduces redundant exploration while preserving mobility, leading to an optimal trade-off between spatial order and persistence. In a strong-memory regime, long-lived chemical trails induce effective self-avoidance, strongly suppressing revisits and long search times. Here, optimal search occurs at finite memory strength: Permanently persistent trails lead to self-caging, while moderate memory enables efficient exploration. At higher densities, overlapping chemical trails give rise to a collective self-avoidance mechanism that yields substantial cooperative speedup without global spatial order. Together, these results show how chemically mediated memory and interactions can optimize collective search across distinct dynamical regimes.

We theoretically investigate the collisions between ultracold polar molecules in the presence of two lasers ensuring a Raman resonant transition on individual molecules to suppress photon scattering, taking the example of bosonic ${}^{23}\mathrm{Na}{}^{39}\mathrm{K}$ molecules. By varying laser detunings and intensities, we enable a repulsive long-range interaction potential between molecules. After solving a set of coupled Schrödinger equations with the Hamiltonian written in the basis of laser-dressed states of the molecule pair at infinite distance, we identify quasiresonant conditions under which elastic collisions are favored over inelastic and reactive ones, by a factor of about 2, thus demonstrating a promising pathway for efficient two-photon optical shielding of ultracold molecular collisions. The results are analyzed in terms of scattering length of the colliding laser-dressed molecules, which exhibit prominent resonances assigned to the interaction of the entrance channel with other specific channels, consistent with the existence of a quasibound level of the long-range molecular pair induced by the lasers.

In this work, we present a numerical and experimental investigation of the collective early-time decay rates of an optically dense cold atomic cloud supporting a large number of excitations. We prepare the atomic ensemble by driving the system to its steady state with varying Rabi frequencies $\mathrm{\Omega }$ that go from the low excitation $\mathrm{\Omega }\ll \mathrm{\Gamma }$ to the multiple excitation regime $\mathrm{\Omega }\gg \mathrm{\Gamma }$, where $\mathrm{\Gamma }$ is the single-atom decay rate. We investigate the early-time dynamics in the transition between the strong and weak driving regimes using (1) angular-dependent observables, such as the light emitted by the cloud, and (2) global observables, i.e., the excited-state population. When driving the cloud on resonance, we find that as a function of the driving frequency, the behavior of the collected light at certain angles transitions from the single-photon subradiant regime to a superradiant regime, while the behavior of the excited-state population does not show superradiance. The experiment shows good agreement with numerical predictions at the chosen angle of observation in the regime of parameters under study.

We study dynamical correlations of interacting hard-core anyons on a one-dimensional lattice at infinite temperature. This is a setting in which the many-body spectrum is independent of the statistical phase $\theta$, while dynamical correlators remain sensitive to $\theta$ through nonlocal Jordan-Wigner strings. We compute single-particle Green's functions, spectral functions, and density-density correlators, thereby separating the effects of fractional statistics on one-body coherence from those on density transport in a maximally mixed ensemble. In the noninteracting case $V=0$, high-temperature averaging leads to inversion-symmetric Green's functions for all $\theta$ despite the presence of anyonic strings. Finite nearest-neighbor interactions $V$ generate, however, a pronounced left-right asymmetry in the Green's functions for $0<\theta <\pi$, with the strongest chirality appearing at intermediate couplings $V\sim J$ where interactions and hopping compete most effectively. In this regime, the Green's function decays exponentially in time with a statistical-angle-dependent decay rate. At strong coupling, the dynamics crosses over to an atomic-limit regime in which the dependence on $\theta$ is reduced. Here, the Green's function decays universally as $t^{-1}$ and the corresponding spectral function displays a three-band structure. In contrast, density-density correlations are insensitive to statistics and recover the known infinite-temperature transport regimes of the XXZ chain, including ballistic, superdiffusive, and diffusive behaviors. These results identify dynamical correlation functions as direct probes of fractional statistics in high-entropy quantum systems.

We show that Andreev spin qubits can be realized in a Josephson junction based on the helical edge states of a two-dimensional topological insulator (quantum spin Hall system) proximized by superconducting films, in the presence of magnetic doping. We demonstrate that the electric dipole transitions between the Andreev spin states induced by the magnetic doping can be harnessed to manipulate the Andreev spin qubit by microwave radiation pulses, without applying an external Zeeman field or invoking ancillary states. We numerically simulate the realization of not and Hadamard quantum logic gates, and discuss implementations in realistic setups.