Wave energy holds immense potential, yet to date progress has been hampered by substantial design challenges and perceived high levelized cost of electricity (LCoE). Control strategies could be vital for improving the economic viability of wave energy converters (WECs), yet practical implementations demonstrating performance remain limited. Here, we present, and implement experimentally for the first time, a self-sufficient control system requiring no external measurements. It is physically demonstrated for the complex hinged, Moored, MultiMode, Multifloat WEC, called M4. The controller operates within a linear noncausal framework to optimize generator torque, where excitation forces are estimated and predicted autoregressively. A real-time state-space hydrodynamic model, based on the Cummins-type linear diffraction-radiation formulation, enables operation based solely on motor-generator torque-speed data. In a first-of-its-kind wave basin experiment, the control strategy is shown to over double energy capture (up to a 125% increase) whilst also demonstrating performance in both unidirectional and directionally spread irregular wave conditions, mimicking real ocean complexity. Site-specific assessment across four European wave sites demonstrates substantial implications for system design and performance: The optimal device size is approximately $40\%$ less than that defined by the average peak period of a site, as often used, and with control implemented, the average power per unit mass (approximately proportional to the inverse of LCoE) increased by about $100\%$ across the four sites. This represents a step change toward the commercial viability of wave energy.

A referential example of a physical system that supports bound states in the continuum (BICs) with an infinite quality factor ($Q$ factor) is a metasurface of discrete scatterers (resonators), whose response can be significantly modified by exploiting lattice interactions. In this work, we explore the multipole-interference mechanism for realizing accidental acoustic BICs (trapped modes) at $\mathrm{\Gamma }$ point (in-plane Bloch wave vector ${\mathbf{k}}_{\parallel }=\mathbf{0}$) of biperiodic metasurfaces of acoustic resonators with one resonator per unit cell. To do so, we expand the pressure field from the metasurface into a series of scalar zonal ($m=0$) spherical multipoles, carried by a normally incident plane wave, and formulate analytical conditions on the resonator multipole moments under which an eigenmode becomes a BIC. The conditions enable us to determine the lattice constant and frequency values that facilitate the formation of an axisymmetric BIC with a specific parity, resulting from destructive interference between zonal multipoles of the same parity, despite each moment radiating individually. By employing the T-matrix method for acoustic metasurfaces, we numerically investigate the BIC resonance in various structures, including finite arrays, and also the transformation of such resonances into high-$Q$ quasi-BIC regimes, which can be excited by a plane wave at normal incidence.

We show that the expectation values of operators of multiparticle systems consist of two contributions: (1) one that solely involves probabilities and (2) one arising from interference. We demonstrate that a nonvanishing interference contribution is necessary to either surpass classical bounds, such as the Clauser-Horne-Shimony-Holt border, or create contradictions to classical predictions, as in the Greenberger-Horne-Zeilinger scenario.

The practical application of quantum technologies to chemical problems faces significant challenges, particularly in the treatment of realistic basis sets and the accurate inclusion of electron correlation effects. A direct approach to these problems is currently infeasible due to limitations in the number of logical qubits, their fidelity, and the shallow circuit depths supported by existing hardware, all of which hinder simulations at the required level of accuracy. A promising alternative is hybrid quantum-classical computing, where classical resources are used to construct effective Hamiltonians characterized by dimensions that conform to the constraints of current quantum devices. In this paper, we demonstrate the performance of a hybrid approach: coupled cluster downfolded Hamiltonians are first evaluated in reduced-dimensionality active spaces, and the corresponding ground-state energies are subsequently computed using quantum algorithms. Our comprehensive analysis explores the achievable accuracy in recovering correlation energies when hundreds of orbitals are downfolded into a problem size tractable by today’s quantum hardware. We argue that such flexible hybrid algorithms, where problem size can be tailored to available quantum resources, can serve as a bridge between noisy intermediate-scale quantum devices and future fault-tolerant quantum computers, marking a step toward the early realization of quantum advantage in chemistry.

We present a technique for cooling arbitrary charged particles in a Penning trap by utilizing self-cooled electrons stored in a separate, macroscopically distant Penning trap as the cooling medium. The electrons decay predominantly to their motional ground state by emission of cyclotron radiation, which results in extremely low temperatures in the realm of single-digit quantum numbers in the motional degrees of freedom of the sympathetically cooled particle species. This opens up an exciting frontier of tests of fundamental physics in Penning traps. This article provides a conceptual overview as well as a quantum-mechanical description of the involved cooling dynamics. The first implementation of this technique is currently being realized at the dedicated ELCOTRAP experiment at the Max Planck Institute for Nuclear Physics, which introduces special features for a quick iterative technical development cycle. Its current status, first results from commissioning, and future prospects will be presented.

A central goal in the foundations of physics is to understand the structure of physical theories, such as quantum theory, from physical principles. This is often explored by considering various information-theoretic principles. Here, we initiate a similar approach considering relativistic causality principles. No superluminal causation (NSC) and no superluminal signaling (NSS) are distinct relativistic principles, requiring respectively that causal influence/the ability of agents to signal are within the future lightcone. After formalizing their distinction, we investigate how well theories constrained by NSC and NSS perform in a task that involves generating nonclassical correlations. We find a spacetime configuration in which this task cannot be achieved in any theory (classical, quantum, or postquantum) satisfying NSC. However, we show that theories violating NSC but satisfying NSS can perfectly achieve the task. We give a protocol that would, in a world allowing superluminal causation, enable its operational certification without violating NSS, in general spacetimes. In the case of (1 + 1)-dimensional Minkowski spacetime, the task remains achievable in a configuration where measurement outcomes occur arbitrarily earlier in time than the settings, allowing a form of certifiable retrocausality without violating NSS. We illustrate our results by linking two different types of nonclassical postquantum resources: PR boxes and jamming. Our work offers insights into the role of different relativistic causality principles in fundamental physics and paves the way for characterizing the information-theoretic structure of theories obeying such principles.

OH radical can be found in comets, stellar atmospheres, planetary atmospheres, interstellar clouds, exoplanets, the solar photosphere, and sunspots, making it a significant astrophysical molecule. Its detection relies on its emission properties, intrinsic to the molecules’ rovibrational levels. This work presents high-level ab initio calculations of the electronic structure of OH radical using complete active space self consistent field/multiReference configuration interaction calculations, including Davidson correction methods with large basis sets and extensive treatment of the electron correlation. The adiabatic potential energy curves of the low-lying doublet and quartet electronic states of the hydroxyl, in the representation ${}^{2\mathrm{S}+1}{\mathrm{\Lambda }}^{\left(+/-\right)}$, are investigated. Additionally, a systematic investigation of the transition dipole moment function (TDMF) for the $\mathrm{B}{}^2\mathrm{\Sigma }^{+}-\mathrm{X}{}^2\mathrm{\Pi }$ and $\mathrm{D}{}^2\mathrm{\Sigma }^{-}-\mathrm{X}{}^2\mathrm{\Pi }$ transitions has been done along with the Franck-Condon factors of these systems. The computed TDMF and potential energy function are used in Le Roy's LEVEL and Western's PGOPHER programs, in combination with experimental literature line positions, to calculate rovibronic $\mathrm{B}{}^2\mathrm{\Sigma }^{+}-\mathrm{X}{}^2\mathrm{\Pi }$ and $\mathrm{D}{}^2\mathrm{\Sigma }^{-}-\mathrm{X}{}^2\mathrm{\Pi }$ transitions. The corresponding “first principles”-based line lists include line intensities, line positions with the relevant quantum numbers of the upper and lower states, e/f parity, and Einstein $A$ coefficients. The results show good agreement with previously published experimental and theoretical data, including a corresponding updated MARVEL (measured active rotational-vibrational energy levels) analysis of the lowest excited states of the OH molecule.

Phase separation, the spontaneous segregation of density, is a ubiquitous phenomenon observed across diverse physical and biological systems. Within a crowd of motile elements, active phase separation emerges from the interplay of activity (i.e., self-propulsion) and density interactions. A striking feature of active phase separation is the persistent formation of dilute-phase bubbles within the dense phase, which has been explored in theoretical models. However, the fundamental parameters that systematically control bubble formation remain unclear in conventional self-propelled particle models. Here, we introduce an active binary mixture model in which solutes and solvents dynamically exchange positions on a lattice; both solutes and solvents are self-propelled particles, but solvents play a role analogous to empty space in typical dry active matter. Within this model, we find that spontaneous bubble formation of solvents can be tuned by activity asymmetry, which is the difference between the solute and solvent activities. Numerical simulations reveal that moderate solvent activity enhances bubble formation, while larger solvent activity, comparable to solute activity, suppresses it. By employing mean-field theory, which captures essential phase behaviors, we consider the mechanism for the enhancement of bubble formation induced by solvent activity. Beyond these findings, when solute and solvent activities are equal, we apply the finite-size scaling analysis to estimate the critical exponents for active phase separation under the suppression of bubbles. Our findings establish activity asymmetry as a key control parameter for active matter phase transitions, offering insights into universality in nonequilibrium systems.

Attosecond-pump attosecond-probe spectroscopy (APAP) is the key to understanding electronic-dominated dynamics in light-matter interactions. Although the feasibility of APAP has been demonstrated using isolated attosecond pulses (IAPs), the efforts are mainly confined to the ionization-induced dynamics triggered by the extreme ultraviolet and soft x-ray lights. However, the generation of IAPs capable of exciting neutral electronic excited states, which are more prevalent in nature, is still in its infancy, significantly limiting comprehensive insights into valence-electron wave packet dynamics. Here, we theoretically demonstrate a scheme for the straightforward and compact generation of white-light IAPs covering the visible and ultraviolet regions, based on solid-state high-harmonic generation. By analyzing the strong-field-induced electron-hole dynamics together with a saddle-point approximation, we unfold its microscopic generation mechanism. Furthermore, the feasibility and robustness of this approach are validated by the generation of IAPs from various materials under the same mechanism. Our work paves the way for generation of tabletop white-light IAP sources, thereby harnessing the widespread applications of APAP.

We investigate GaAs/AlGaAs heterostructure membranes with a metasurface made up of a grating of two-dimensional electron system strips. Experiments have revealed a strong plasma resonance in the transmission of the metasurface. We have found that a collective effect from the superlattice, along with lateral screening between the strips, leads to the emergence of a plasmon mode in the metasurface under study. Furthermore, we develop an analytical approach that accurately describes the behavior of the discovered superlattice plasmon mode, providing insights into the fundamental physics of plasmonic metasurface systems.

Snap buckling is a rapid shape transition in slender structures, appearing as a fundamental switching mechanism of natural and man-made systems. Boundary conditions of structures are crucial to predict and control their snap buckling behavior. However, the general framework that relates boundary conditions, geometry, and performance of structures is still absent to date. Here, we study the snap buckling of hemispherical shells in contact with rigid cylinders of different diameters to uncover the roles of boundary conditions in dynamic performance of shells. Specifically, we analyze the jumping dynamics of the pneumatically inverted shells placed on the rigid cylinder by combining experiments and analytical theory. We find the characteristic diameter of the cylinder determined from the shell geometry that can switch between continuous and discontinuous buckling associated with the jumping behavior. The analytical predictions for jumping performance of the shell supplemented with the characteristic diameter are in excellent agreement with our experimental results. Our study clarifies that contact geometry is crucial in predicting the pathway of snap buckling, indicating that dynamic performance of soft robots would be optimized by tuning their surface geometry.

Gas phase ultrafast electron diffraction (GUED) has become a powerful technique to directly observe the structural dynamics of photoexcited molecules. GUED reveals information about the nuclear motions that is complementary to the information on the electronic states provided by spectroscopic measurements. GUED experiments so far have utilized a single laser pulse to excite the molecules and an electron pulse to probe the dynamics. This limits the excited states that can be studied to only those that can be reached by absorption of a photon from the ground state or in some cases simultaneous absorption of multiple photons. A broader class of experiments and dynamics can be accessed using two time-delayed laser pulses to access unexplored regions of the potential energy surfaces. As a proof-of-principle experiment using a double excitation, we studied the photodissociation of trifluoroiodomethane molecules that are pre-excited with an infrared (800 nm) femtosecond laser pulse before photodissociation is triggered with an ultraviolet (266 nm) femtosecond laser pulse. We have observed significant differences in the dissociation dynamics, with pre-excitation resulting in a slower dissociation process. This capability can offer insights into the evolution of nuclear wave packets in regions of the excited potential energy surface that are inaccessible in single-photon excitation. We present a methodology to carry out the measurement, analyze, and interpret the data that could be applied to a broad class of experiments.

We investigate resonance-enhanced high-harmonic generation (rHHG) in ${\mathrm{Cr}}^{+}$ by comparing a one-dimensional (1D) shape-resonant model, time-dependent density functional theory (TDDFT), and independent particle approximation (IPA) simulations. Previous studies linked rHHG to the $3p\to 3d$ giant resonance, suggesting a modified four-step model where recolliding electrons are first captured in the autoionization state before recombining into the ground state, potentially leading to an emission delay associated with the resonance lifetime. While both the 1D model and TDDFT reproduce experimental spectra, TDDFT reveals that rHHG counterintuitively originates from spin-down $3p$ states, while spin-up $3d$ electrons negligibly contribute. The IPA fails to reproduce rHHG, highlighting the significance of electron correlations. Furthermore, TDDFT revealed a correlation-induced $\sim 480$ as time delay, accompanied by a strong phase shift across the resonance, potentially explaining earlier reconstruction of attosecond beating by interference of two-photon transitions measurements. Our work sheds light on long-standing open questions in rHHG and should advance ultrafast spectroscopies of electron correlations and resonances.

The spread of ideas, behaviors, and technologies generally depends on feedback mechanisms operating across multiple scales. Previous studies have extensively examined pairwise transmission and local reinforcement. However, the role of macro-level social influence—where widespread adoption enhances further adoption—remains understudied. Here, we focus on a contagion process that incorporates both pairwise interactions and macro-level reinforcement. We show that the contagion undergoes a shift from continuous to mixed-order transition as macro-level influence exceeds a reinforcement threshold. Simulations on various real-world networks indicate that network localization governs the contagion outcomes by determining the critical point and the reinforcement threshold. Building on this insight, we develop a structural metric linking network localization to contagion dynamics, revealing a key trade-off: Networks that facilitate weak contagion tend to experience slower diffusion and lower adoption rates, while networks that suppress weak contagions enable faster and more widespread adoption. These findings challenge the conventional belief that stronger local connectivity uniformly promotes contagion.

The coherence of light from independent ensembles of elementary atomic emitters plays a paramount role in diverse areas of modern optics. We demonstrate the interference of photons scattered from independent ensembles of warm atoms in atomic vapor. It relies on the feasibility of the preservation of coherence of light scattered elastically in the forward and backward directions from Doppler-broadened atomic ensembles, such that photons with chaotic photon statistics from two opposite atomic velocity groups contribute to the same detection mode. While the random phase fluctuations of the scattered light caused by a large thermal motion prevent direct observability of the interference in the detected photon rate, the stable frequency difference between photons collected from scattering off counterpropagating laser beams provides strong periodic modulation of the photon coincidence rate with the period given by the detuning of the excitation laser from the atomic resonance. The presented interferometry represents a sensitive and robust methodology for Doppler-free optical atomic and molecular spectroscopy based on photon correlation measurements on scattered light.

Swarmalators constitute a paradigmatic model for understanding the collective dynamics of coupled moving agents, integrating both internal and spatial degrees of freedom. Empirical evidence from systems such as bird flocks and living matter highlights the relevance of topological, metric-free coupling, but their impact on swarmalator dynamics remains largely unknown to date. Here, we present and analyze a topological swarmalator model in which the units interact topologically, on Delaunay networks. We find intriguing self-organized collective dynamics, including patterns with local vortices and unprecedented spatiotemporal patterns absent in metric-based models. Identifying three order parameters to quantify synchrony, spatial order, and vortex formation, we map the phase diagram that classifies these diverse patterns. Notably, we uncover a first-order transition even if the phases of all units are frozen, a dynamics inverted relative to the classical Kuramoto model. These insights not only advance our theoretical understanding of locally coupled systems of moving agents, but also offer key guidelines for their control.