Strong-field ionization provides a fundamental route for probing nonlinear electron dynamics on ultrafast timescales, but it has been explored almost exclusively with classical coherent driving fields. Intense quantum light sources, particularly bright squeezed vacuum (BSV), now make it possible to ask how macroscopic photon-number fluctuations affect nonperturbative electron emission. Here, we address this question by performing shot-resolved BSV-photoelectron coincidence measurements in strong-field ionization of xenon atoms, with simultaneous access to the single-shot driving pulse intensity and the energy- and momentum-resolved photoelectron response. By calibrating the intensity-dependent ionization probability with a pulse-integrated Ammosov-Delone-Krainov response, we reconstruct the single-pulse ionization-yield distribution and quantify its fluctuations in electron momentum space. We find that intensity-conditioned BSV-driven spectra recover coherent-field-like cutoff scaling, while the reconstructed yield fluctuations increase toward higher electron energies and momenta, showing that high-energy electrons preferentially sample rare high-intensity BSV shots. Beyond ensemble-averaged spectra or photoelectron-number statistics, this approach resolves the momentum- and energy-dependent transfer of quantum-light fluctuations into atomic ionization yields. These results establish yield fluctuations as observables for strong-field quantum optics and benchmarks for theories beyond the classical-field approximation.

High-overtone bulk acoustic wave resonators (HBARs) promise advanced phononics, yet achieving nonlinearity remains challenging. We demonstrate a radiation-pressure-type parametric interaction between GHz HBARs and low-frequency flexural modes in a suspended silicon nitride membrane, where mechanical displacement modulates the external dissipation rate to enable dissipative acousto-mechanical coupling. Benefiting from the high quality factor, the system enters the resolved-sideband regime at room temperature, yielding acousto-mechanically induced transparency. We observe tunable Kerr nonlinearity and generate coherent HBAR frequency combs via two-tone driving. Notably, our dissipative coupling strength is 20 times larger than the dispersive coupling, the highest ratio among reported hybrid dissipative-dispersive coupling systems, resulting in the experimental observation of amplification in the reflection spectra under red-sideband driving. The ability to interface dense HBAR modes with a common mechanical resonator provides a scalable on-chip platform for multimode phononic information processing, with quantum phononics potentially achievable at sub-Kelvin temperatures.

In low-luminosity active galactic nuclei like M87* and Sgr A*, the accretion disk around the central supermassive black hole is tenuous and collisionless. As a result, the usual ideal magnetohydrodynamics approximation may not be applicable. In this Letter, we report on the first fully kinetic simulations of the accretion process where the plasma initially has finite angular momentum, focusing on the case of axisymmetry. The simulated accretion flow behaves remarkably similarly to the magnetically arrested disk regime of ideal magnetohydrodynamics, reproducing episodes of magnetic flux saturation and eruption typical of magnetically arrested disks. The resemblance to fluid models owes largely to kinetic instabilities, which regulate pressure anisotropy in the disk, allowing fluid terms to dominate the angular momentum transfer. In addition, by handling vacuum regions effectively, our kinetic approach probes the matter supply to the jet funnel. We observe no efficient penetration of the accreting material into this region, suggesting that a pair discharge may be required to sustain the Blandford-Znajek process. These initial findings represent important groundwork to be checked and built upon by future kinetic accretion simulations, especially in 3D.

Biological valves control the directionality of oscillatory or fluctuating internal flows by deforming (reversibly) to stop flow. To uncover the physical basis for flow rectification in these systems, we introduce a simple physical mimic of the mitral heart valve that is shaped like a soft conical shell in an impinging flow. Combining ex vivo porcine-heart and in vitro conical valve experiments, we show how noise-activated buckling deformations serve to rectify the flow. We quantitatively explain our observations using a minimal elastohydrodynamic theory for valve closure that leads to a dynamical bifurcation driven by stochastic hydrodynamic forces. Our theory also suggests that valve collapse can be triggered on demand, which we corroborate using experiments. Together, these results suggest a design principle for the efficient operation of soft valves.

Spinning is widely used in nature and industry to form thin solid fibers from a liquid. While the fiber radius is readily determined when draw speed is controlled, many situations involve a draw force, making fiber radius difficult to predict. Here, we take advantage of a gravity-stretched jet configuration with tunable light-induced solidification, to elucidate spinning dynamics for a sharply localized liquid-to-solid transition. We show and explain how light intensity and solidification kinetics control the solidification locus, which opens routes for characterizing fast solidification kinetics. We also determine how the fiber radius, the transient regime following light switch-on and jet stability are set by gravity, inertia, and capillarity. These results offer predictive control on the spun solid (fiber versus beads), including for intermittent solidification.

Graphene-based moiré superlattices exhibit novel quantum phenomena driven by pronounced interactions, leading to topological correlated states like orbital Chern insulators exhibiting quantum anomalous Hall effects. Typically, intrinsic Chern insulators are stabilized at odd moiré fillings, as even fillings often result in valley-balanced, topologically trivial states at zero magnetic field. In this Letter, we report the observation of a Chern insulator with $C=1$ state at moiré filling $\nu =2$ in the rhombohedral octalayer graphene/hexagonal boron nitride moiré superlattice. In the vicinity of this topological phase, we also observe a robust topologically trivial correlated insulator at the same filling, highlighting the intense competition between different ground states. Observing such a Chern insulator, in particular with $C=1$ at $\nu =2$ is intriguing, as the lowest moiré band in each flavor is expected to host Chern number $C=1$ or $-1$. We further demonstrate that such a state could originate from the hybridization between the low-energy moiré flat bands and high-energy remote bands in a single flavor by self-consistent Hartree-Fock calculation. Our findings extend the known topological phase diagram of rhombohedral multilayer graphene moiré systems and establish this platform as highly promising for investigating strong electron correlations and multiband hybridized transport at fillings higher than $\nu =1$.

In the context of quantum electrodynamics, a strong electric field can trigger the production of particle-antiparticle pairs, a phenomenon known as the Schwinger effect. In practical experimental scenarios, producing a pair requires quantum tunneling of particles over a long distance, thus suppressing the production rate and making this process very challenging to observe. Here we report an experimental investigation, in a cold-atom quantum simulator, of the effect of the external background field on pair production from the infinite-mass vacuum in a $1+1\mathrm{D}$ U(1) lattice gauge theory in its quantum link model formulation, which we address through a genuine out-of-equilibrium protocol. The ability to tune the background field allows us to study pair production in a favorable regime of a large production rate. Furthermore, we probe the time evolution of the model in the zero fermion mass limit. We find that the energy spectrum of the time-evolved observables displays excitation peaks analogous to the (massive) bosonic modes of the Schwinger model and whose phenomenology can be interpreted as a string inversion mechanism. Our Letter opens the door to quantum-simulation experiments that can controllably tune the production of pairs and manipulate their far-from-equilibrium dynamics.

Steady shearing and planar extension are commonly viewed as two distinct types of flow field, especially in the context of probing the rheology of complex fluids. By leveraging the kinematic equivalence between the two flows, we derive an effective extension rate experienced by a material element which removes the rotational component of the shearing flow. This enables reconstruction of the steady planar extensional viscosity of an unknown fluid using only material functions measured in a steady shearing flow, revealing a deep rheological equivalence between the two deformation histories. We demonstrate this equivalency through phenomenological and microscopically motivated frame-invariant constitutive models as well as using experimental data obtained with a viscoelastic polymer solution and a polymer melt.

Recent experiments revealed a strong dielectric anisotropy in nanoconfined water, with a giant in-plane dielectric constant exceeding ${10}^3$ and an ultralow out-of-plane response of order 2–3, far beyond the predictions of conventional continuum electrostatics. A pronounced enhancement of in-plane electrical conductivity was also observed under strong confinement. Here, we develop a unified microscopic theory showing that these anomalies arise from confinement-induced anisotropic polarization correlations in the hydrogen-bond network. Starting from linear-response theory with an exponential polarization-correlation kernel, we show that nanoconfinement selectively enhances longitudinal in-plane dipolar correlations while suppressing perpendicular fluctuations. This leads to universal scaling laws for the dielectric response, $\kappa (h)\propto {\xi }_c^{2}f(h/2{\xi }_c)$, and the conductivity, $\sigma (h)\propto \kappa (h)/h$, where ${\xi }_c$ is the confinement-enhanced dipolar correlation length. The resulting growth of in-plane correlations and suppression of out-of-plane fluctuations naturally explain the giant in-plane and ultralow out-of-plane dielectric constants, as well as the enhanced in-plane conductivity. Quantitative agreement with experiment over a broad range of channel thicknesses establishes nanoconfined water as a ferroelectriclike correlated polar fluid governed by collective dipolar fluctuations rather than simple geometric capacitance effects.

Despite the rapid development of quantum science and technology, errors are inevitable and play a crucial role in quantum simulation and quantum computation. In quantum chaotic systems, coherent errors arising from imperfect Hamiltonian control and incoherent errors induced by coupling to the environment are both exponentially amplified during time evolution due to information scrambling. A fundamental question is how these two classes of errors imprint distinct signatures on the emergent irreversibility of many-body dynamics. In this Letter, we address this question by investigating multiround time-reversed dynamics in the presence of both coherent and incoherent errors. By applying scramblon theory, we obtain closed-form expressions for the Loschmidt echo over different rounds of time-reversed evolution. For incoherent errors, the error accumulates linearly with the number of rounds, whereas coherent errors exhibit a crossover from quadratic to linear accumulation. These predictions are explicitly verified using the solvable Sachdev-Ye-Kitaev model. Our results provide a theoretical foundation for characterizing and calibrating coherent and incoherent errors in reversed dynamics, with particular relevance to nuclear magnetic resonance systems.

The intertwining of charge, spin, and lattice degrees of freedom underlies the emergent properties of correlated materials. A recent prominent example is the kagome metal FeGe, which hosts a charge density wave (CDW) within a preexisting antiferromagnetic state. Although partial Ge-Ge dimerization is known to accompany CDW formation, the thermodynamic pathway through which long-range CDW order emerges remains unclear. Using temperature-dependent high-resolution x-ray diffraction measurements, we observed a robust splitting of the lattice reflection into two coexisting peaks with distinct lattice parameters in FeGe crystals exhibiting long-range CDW order at the CDW transition temperature. In addition, the long-range CDW order emerges concurrently and remains commensurate with a structural phase characterized by the smaller out-of-plane lattice parameter. Our observation provides direct evidence for a first-order structural phase transition coupled to long-range CDW order, which is absent in samples exhibiting short-range CDW order. A Landau model shows that strong charge-lattice coupling is a key factor in stabilizing the long-range CDW order. Our Letter reveals that the first-order structural phase transition is crucial for stabilizing long-range CDW order, suggesting lattice strain as a tuning parameter for controlling intertwined electronic states in kagome metals.

While the Hofstadter butterfly is commonly observed in moiré superlattices, its thermal properties have not been investigated, particularly the quantized heat flow expected for Chern insulators. Here we report the first thermal transport measurements in a graphene and hexagonal boron nitride moiré superlattice under high magnetic field. We observe a quantized heat flow, uniquely set by the topological invariant, for all investigated states of the Hofstadter butterfly: quantum Hall states, Chern insulators, and even symmetry-broken Chern insulators emerging from strong electronic interactions. Our work firmly establishes the universality of the quantization of heat transport and its intimate link with topology.

We demonstrate atom-photon entanglement using a single cesium atom trapped in an optical tweezer. Entanglement is generated by resonant excitation and subsequent spontaneous decay, which entangles the atomic Zeeman state with photon polarization. The emitted photon is coupled into a single-mode fiber, enabling measurement of the Bell-state fidelity. We obtain raw entanglement fidelity of $\mathcal{F}=0.942(16)$ and inferred fidelity of ${\mathcal{F}}_{\inf }=0.962(26)$ after correcting independently characterized atom measurement errors. Compared with related free-space experiments using ${}^{87}\mathrm{Rb}$, the Zeeman substructure of the relevant excited level in ${}^{133}\mathrm{Cs}$ requires the use of a single short excitation pulse in each entanglement attempt in order to suppress unwanted re-excitation. These results establish a free-space ${}^{133}\mathrm{Cs}$ atom-photon interface and provide a step toward dual-species Rb-Cs quantum networking.

The first observation of a new meson state decaying into $B_c^{+}$ and a photon is presented using a dataset of $pp$ collisions at a center-of-mass energy $\sqrt{s}=13\mathrm{TeV}$ collected by the ATLAS detector at the Large Hadron Collider, corresponding to an integrated luminosity of $140{\mathrm{fb}}^{-1}$. The $B_c^{+}$ mesons are reconstructed from a three-muon final state from $B_c^{+}\to J/\psi ({\mu }^{+}{\mu }^{-}){\mu }^{+}{\nu }_{\mu }X$ decays, along with photons reconstructed via conversions to electron-positron pairs in the detector material. The new state is observed with a significance that exceeds 8 standard deviations. The mass difference between the new meson state and the ground-state $B_c^{+}$ meson is measured to be $64.5\pm 1.4(\mathrm{stat}){}_{-1.4}^{+1.0}(\mathrm{syst})\mathrm{MeV}$. This corresponds to a mass for the observed state of $6339.0\pm 1.4(\mathrm{stat}){}_{-1.4}^{+1.0}(\mathrm{syst})\pm 0.3(m_{B_c^{+}})\mathrm{MeV}$, where the last uncertainty is due to the precision of the best knowledge of the $B_c^{+}$ meson mass. The low mass difference value matches the theory expectations for the lowest vector state of the $\overline{b}c$ system, the $B_c^{*+}$ meson.

Real-world systems often evolve on different timescales and possess multiple coexisting stable states. Whether or not a system returns to a given stable state after being perturbed away from it depends on the shape and extent of its basin of attraction. We show that basins of attraction in multiscale systems can exhibit special geometric properties in the form of singular funnels. Although singular funnels are narrow, they can extend to different regions of the phase space and, unexpectedly, impact the system’s resilience to perturbations. Consequently, singular funnels may prevent common dimensionality reductions in the limit of large timescale separation, such as the quasistatic approximation, adiabatic elimination, and time averaging of the fast variables. We refer to basins of attraction with singular funnels as singular basins. We show that singular basins are universal and occur robustly in a range of multiscale systems: the normal form of a pitchfork bifurcation with a slowly adapting parameter, an adaptive active rotator, and an adaptive network of phase rotators.

This Letter presents a combination of searches for Higgs boson pair ($HH$) production performed by the ATLAS and CMS Collaborations using proton-proton collision datasets recorded at $\sqrt{s}=13\mathrm{TeV}$ during the Large Hadron Collider Run 2, corresponding to integrated luminosities ranging between 126 and $140{\mathrm{fb}}^{-1}$. The upper limit at the 95% confidence level on the total $HH$ signal strength, defined as the ratio of the measured cross section to the standard model (SM) prediction, corresponds to 2.5, with an expected value of 1.7 (2.8) assuming the absence (presence) of the SM $HH$ signal. The strength of the $HH$ signal is measured to be ${0.8}_{-0.7}^{+0.9}$ relative to the SM prediction. The observed significance is found to be 1.1 standard deviations whereas 1.3 are expected for the SM $HH$ signal. Constraints are set on the Higgs boson trilinear self-coupling and on the couplings of two Higgs bosons to two vector bosons, both normalized to the SM predictions and denoted as ${\kappa }_{\lambda }$ and ${\kappa }_{2V}$, respectively. The observed individual constraints at the 95% confidence level are $-0.71<{\kappa }_{\lambda }<6.1$ and $0.73<{\kappa }_{2V}<1.3$, while the expected constraints assuming the presence of the SM $HH$ signal are $-1.3<{\kappa }_{\lambda }<6.7$ and $0.66<{\kappa }_{2V}<1.4$.

Unconventional superconductivity is a desirable state of matter due to its potential for high transition temperatures $T_{\mathrm{c}}$ and associated favorable superconducting properties. However, the sign-changing nature of the order parameter of unconventional superconductors renders their condensates fragile to disorder, an inevitability in real materials. We uncover the generic properties of electronic band structures and associated Bloch weights able to support robust unconventional superconductivity. We demonstrate this property in several case studies of the kagome and Lieb lattices, showing how unconventional superconductors exhibit unusually weak $T_{\mathrm{c}}$ suppression by disorder, despite featuring fully compensated sign-changing order parameters. We contrast these results with those for unconventional superconductivity on the square and honeycomb lattices, which are unable to protect the condensates from disorder. Finally, we discuss material candidates for which this effect may be realized.

In the heavy-fermion metal ${\mathrm{YbRh}}_2{\mathrm{Si}}_2$, quantum criticality at a suppressed antiferromagnetic order is governed by the interplay of local magnetic moments and itinerant conduction electrons. We demonstrate how this can be investigated by a new experimental approach that enables the observation of electron spin resonance (ESR) across a broad range of frequencies and fields at very low temperatures. This allowed us to cover a large part of the phase diagram from the paramagnetic Fermi-liquid phase to the phase with antiferromagnetic order and including the quantum-critical regime. Both the ESR $g$ factor and the linewidth present distinct behaviors in these three regimes, providing further insight into the physics across a quantum critical point. Notably, when cooling down at a field directly toward the quantum critical point, both $g$ factor and linewidth continuously decrease. Furthermore, we observe a very good matching of the $g$-factor behavior upon field tuning and temperature tuning toward the quantum-critical point. We analyze and discuss the results in the context of present theories on ESR in strongly correlated electron systems.

Topological insulators are typically characterized by particularly stable properties, such as global invariants, and can be identified by probing their robust surface states. A recently discovered novel form of band topology, delicate topology, challenges this paradigm: its defining property, multicellularity, can be removed by introducing a coupling to local orbitals anywhere in the spectrum, even far above the relevant band gap. This makes it hard to diagnose delicate topology with conventional probes that access only low-energy degrees of freedom. Here, we introduce strong local impurities as a spectroscopic probe of a delicate topological insulator which we realize in a phononic metamaterial. By tuning the impurity strength and performing orbital-resolved readout, we observe recently proposed indicators of topology: ring states, in-gap bound states whose frequencies remain pinned in the strong-impurity limit while avoiding the impurity site in real space. We find that these ring states persist even when the multicellularity in our system is removed by a weakly hybridizing additional orbital. Our results establish strong-impurity spectroscopy as a bulk probe of complex multiband physics, including delicate topological phases.