The generation of entangled photons through spontaneous parametric down-conversion (SPDC) is a critical resource for many key experiments and technologies in the domain of quantum optics. Historically, SPDC was limited to the generation of photon pairs. However, the use of the strong nonlinearities in circuit quantum electrodynamics has recently enabled the observation of three-photon SPDC (3P-SPDC). Despite great interest in the entanglement structure of the resultant states, entanglement between photon triplets produced by a 3P-SPDC source has still not been confirmed. Here, we report on the observation of genuine tripartite non-Gaussian entanglement in the steady-state output field of a 3P-SPDC source consisting of a superconducting parametric cavity coupled to a transmission line. We study this non-Gaussian tripartite entanglement using an entanglement witness built from three-mode correlation functions, observing a maximum violation of the bound by 15 standard deviations of the statistical noise. Furthermore, we find strong agreement between the observed and the analytically predicted scaling of the entanglement witness. We then explore the impact of the temporal function used to define the photon mode on the observed value of the entanglement witness.

Ultracold alkaline-earth atoms and molecules now enable experimental realizations of SU(N)-symmetric Fermi-Hubbard models, yet theoretical understanding of these systems, particularly at finite doping remains limited. Here we investigate the strong-coupling limit of the SU(3) symmetric Fermi-Hubbard model on the triangular lattice across the full doping range. Using a three-flavor extension of Gutzwiller-projected hidden fermion determinant states (G-HFDS), a neural network based variational ansatz, we analyze two- and three-point spin-spin and spin-spin-hole correlations of the SU(3) Cartan generators. We further study the structure of a pair of doped holes for large periodic systems, and compare our results to the paradigmatic SU(2) square lattice equivalent, finding strikingly similar magnetic correlations, non-$s$-wave pairing symmetry, and enhanced binding energies. Our results provide a foundation for future exploration of doped SU(N) Mott insulators, providing insights for both theoretical developments and quantum simulation experiments.

The dispersion of extragalactic fast radio bursts (FRBs) can serve as a powerful probe of the diffuse plasma between and surrounding galaxies, which contains most of the Universe’s baryons. By cross-correlating the dispersion of background FRBs with the locations of foreground galaxies, we can study the relative spatial distributions of plasma and galaxies on scales of 0.1 to 50 Mpc, which are strongly affected by feedback processes in galaxy formation. Here, we present the measurement of the dispersion-galaxy angular cross-power spectrum between 2870 FRBs from the Second CHIME/FRB Catalog and nearly 6 million galaxies from the Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Survey. Over five photometric galaxy redshift bins spanning $0.05<z<0.5$ and at $4.9\sigma$ significance, we make the first definitive detection of spatial correlations in FRB dispersion measure due to cosmic structure. While parameter inferences should be interpreted with caution because of incomplete modeling of both the signal and systematic errors, our data indicate that the plasma-galaxy cross-power spectrum cuts off relative to the matter power spectrum at a scale $k_{\mathrm{cut}}^{-1}=0.84_{-0.34}^{+0.46}\mathrm{Mpc}$. This scale is consistent with those x-ray stacking analyses that suggest dark-matter halos with group-scale masses are largely evacuated of their baryons by feedback processes. Our Letter demonstrates that FRBs are promising tools to discern the physics of baryonic structure formation and will only become more powerful as FRB surveys expand.

Orbital eccentricity is a key tracer of the astrophysical origins of compact binaries; yet it remains absent from routine LIGO-Virgo-KAGRA analyses, in part because of the prohibitive computational cost of generating eccentric template waveforms. The complicated morphology of these waveforms due to the eccentric orbital timescale variations makes it difficult to construct their accurate and efficient surrogate models, especially for waveforms long enough to comprehensively cover the sensitivity bands of current ground-based gravitational-wave detectors. We present a novel and scalable surrogate building technique that makes surrogate modeling of long-duration eccentric binary black hole waveforms both feasible and highly efficient. The technique aims to simplify the harmonic content of intermediate eccentric waveform data pieces by modeling them in terms of an angular orbital element called the mean anomaly, instead of time. We show that this parametrization yields much more compressed surrogates than the standard time-based parametrizations. We also significantly simplify variations in waveform data pieces across the parameter space by expressing them in terms of the instantaneous orbital eccentricity and mean anomaly to ease their parametric fitting. Building on these developments, we construct InspiralESIGMASur: a $2.77\times {10}^{6}M$ (850–1250 orbits) long nonspinning surrogate for the inspiral-only eccentric waveform model InspiralESIGMA [K. Paul et al., Phys. Rev. D 111, 084074 (2025)]. The methods presented in this Letter make it feasible to build long-duration eccentric surrogates for current as well as future third-generation gravitational-wave detectors.

In 2023, after more than two decades of searching, pulsar timing array (PTA) collaborations around the world announced evidence for a stochastic gravitational wave background. It was quickly followed by work from the International Pulsar Timing Array (IPTA), demonstrating that the results of regional collaborations were consistent with each other. The combination of these datasets is still ongoing and represents a significant investment of time and expertise. In that IPTA comparison, authors of this Letter combined the separate datasets in the standard PTA optimal detection statistic for cross-correlations incoherently, that is, the data were combined without fitting a merged timing model across all PTA datasets, treating datasets of the same pulsar as independent, and neglecting the “same pulsar, different datasets” cross-correlations. This Letter refines that method by extending its core ideas beyond detection statistics and into a full, general data-combination method. We have demonstrated its efficacy and extreme efficiency on simulated data. This new method, “FrankenStat,” is very similar in sensitivity and parameter-constraining power to traditional data-combination methods while completing the full data combination in just a few minutes.

Understanding nonlinear saturation of reversed-shear Alfvén eigenmodes (RSAEs) in tokamaks is crucial for high-performance burning plasmas. Employing both nonlinear gyrokinetic simulations and theoretical analyses, we have discovered the novel result that, with energetic particle dynamics kept linear, the nonlinear suppression and eventual saturation of RSAE occur via the downward frequency chirping induced by the beat-driven zonal current. More specifically, as the mode frequency chirps downward, there is enhanced mode conversion to radially propagating electron Landau-damped kinetic Alfvén waves; resulting in enhanced convective (radiative) damping and, thereby, its suppression and saturation. Theoretical results are in good agreement with simulations both qualitatively and quantitatively. This Letter, thus, establishes a fundamental framework for zonal-current mediated saturation of Alfvén eigenmodes in burning plasmas.

Relativistic magnetized shocks are natural sources of coherent radiation, representing a promising framework for fast radio bursts (FRBs). This Letter explores how the radiation reaction (RR) effect, triggered by high-energy photon emissions during shock radiation, significantly alters particle dynamics and coherent radiation properties. Using kinetic particle simulations, we demonstrate that RR severely suppresses electron energies from shock acceleration, resulting in multiple coherent gyration cycles at the shock front. It amplifies the intensity of coherent radiation and boosts energy efficiency by several fold, as compared to the single gyration cycle in the standard model of relativistic magnetized shocks. We further find that the coherent radiation spectrum from RR-mediated shocks is characterized by upshift peak frequency, broaden bandwidth, and narrow spectral peak. These RR-induced radiation changes may be related to several observed FRB phenomena, including the statistically positive correlation between luminosity and bandwidth in repeating and one-off FRBs, the narrow spectra seen in some FRB events, and the bimodal energy distribution reported in FRB 20121102A.

We observe for the first time in silico the transition to a linear regime in the primary damage production in tungsten. As the critical plasma-facing material in fusion reactors, radiation damage in tungsten has been studied extensively in experiments and simulations. Irradiation experiments routinely produce recoils in the MeV range, while full atomistic modeling has been limited to a few hundred keV. Here we bridge these scales with extremely large-scale and accurate machine-learning-driven molecular dynamics simulations with recoil energies up to 2 MeV in systems up to $1\times {10}^9$ atoms. We reveal four regimes of primary damage as a function of damage energy, with a transition to a high-energy regime that deviates from all previous models. Curiously, the start of the high-energy regime coincides with the highest possible recoil energy to tungsten atoms from fusion-emitted neutrons (300 keV).

${\mathrm{H}}_3\mathrm{S}$ sulfur hydride has been widely investigated for its high superconducting critical temperature $T_c$ of 203 K at about $p_c=155\mathrm{GPa}$. Despite being the precursor of superconducting hydrides, a detailed picture of its structural phase diagram in an extended temperature and pressure range is still missing. To determine it with inclusion of both thermal and quantum effects, we carry out path integral molecular dynamics combined to a MACE neural network potential trained on BLYP density functional theory configurations. The resulting ${\mathrm{H}}_3\mathrm{S}$ phase diagram is characterized by the displacive transition between the centrosymmetric $\mathrm{Im}\overline{3}\mathrm{m}$ and polar R3m phases, which originates from a quantum critical point (QCP) located at $p_{\mathrm{QCP}}\approx 134\mathrm{GPa}$. We show that the experimental $T_c$ peak falls into a centrosymmetric region of large nuclear quantum fluctuations above the displacive QCP, as measured by local phonon Green’s functions resolved in imaginary time, where fluctuating moments are at play. We study the critical behavior of the system in the proximity of the QCP by a finite-size scaling analysis, showing that it belongs to the 4D Ising universality class. We finally discuss its implications for the superconducting state.

Magnetic van der Waals materials have mainly been investigated in their bulk form or as few-layer flakes. Because of the challenges in producing atomically thin films, only a few have been isolated as monolayers, which typically exhibit long-range magnetic order below 150 K. In this Letter, we use molecular beam epitaxy to synthesize Co-doped ${\mathrm{Fe}}_5{\mathrm{GeTe}}_2$, achieving precise control over both thickness and composition. We demonstrate ferromagnetism well above room temperature in multilayer samples and present clear evidence of ferromagnetic ordering in monolayers up to $\sim 200\mathrm{K}$. The changes in Curie temperature and magnetic anisotropy as a function of composition exhibit similar trends in both monolayers and thicker films, indicating that the magnetic properties are primarily governed by intralayer magnetic interactions. Through element-specific x-ray magnetic circular dichroism and density-functional theory, we identify the substitution site of Co dopants and reveal the mechanism behind the Curie temperature enhancement induced by Co doping. Our findings suggest that, despite their weak magnetic moment, Co dopants strengthen the magnetic moments on neighboring Fe atoms and enhance the intralayer ferromagnetic exchange interactions.

Quantum metrology promises to surpass classical precision limits by leveraging quantum resources such as entanglement. Maximally entangled Greenberger-Horne-Zeilinger (GHZ) states are theoretically optimal probes for quantum metrology. However, they are fragile to environmental noise, severely limiting their practical utility. To overcome this limitation, we propose and experimentally realize a noise-adaptive quantum metrology scheme that autonomously identifies optimal probes without any prior information of the noise. This is achieved by combining a variational quantum circuit that optimizes available resources with an efficient strategy for evaluating the sensing performance. Using a seven-qubit nuclear spin sensor, we identify optimal probe states that achieve precision improvements up to 0.698 dB over GHZ states when sensing a fixed magnetic field. Furthermore, we show that the learned probe state exhibits cross-parameter robustness, maintaining superior performance over a broad range of magnetic field frequencies. The proposed scheme is model-free, hardware-efficient, and scalable, providing a practical route to noise-resilient quantum metrology on near-term quantum devices.

We construct a simple two-dimensional holographic model of a closed “baby” universe. The baby universe spacetime originates from the black hole interior in Jackiw-Teitelboim gravity. The holographic description is a low-temperature thermal pure state of two Sachdev-Ye-Kitaev (SYK) models. The construction of the state relies on the insertion of a heavy matter operator, which supports the baby universe, together with a first-order thermal phase transition between a black hole phase and an empty anti–de Sitter phase. For the transition, we employ a version of the Maldacena-Qi phase transition of two coupled SYK systems. The bulk entanglement between the anti–de Sitter region and the baby universe remains $O(N)$ below the transition, owing to the large number of light bulk fields. This entanglement admits a definition through coarse-graining over SYK couplings.

We consider the Polyakov loop correlator in the confining phase of large $N$ Yang-Mills theory in three and four dimensions. It can be computed by summing over the exchange of closed flux tubes winding around the thermal cycle. At short separations, the leading divergence is controlled by perturbation theory. Combining these two facts allows us to determine the asymptotic spectral density of string states contributing to the correlator. This sharply relates the weakly coupled UV of the gauge theory to the dynamics of highly energetic flux tubes. Then, in a toy integrable setting, we explore how this can bound the scattering data of the Goldstone modes on top of a long string. We derive a bound on the asymptotic behavior of the reflection amplitude of Goldstones against the flux tube boundary sourced by the Polyakov line, and rule out an asymptotically linear phase shift for the S matrix.

We demonstrate that AI-driven program synthesis can autonomously discover fundamental strategies for decomposing unitary matrices in photonic networks. By extending DreamCoder to complex-valued linear algebra, the system generates decomposition programs achieving the minimal $N(N-1)/2$ Mach-Zehnder interferometers, distinct from both Reck and Clements architectures. Learned programs encode dimension-agnostic invariants: strategies discovered for $5\times 5$ matrices generalize to higher dimensions such as $64\times 64$. The discovered programs encode interpretable, dimension-agnostic construction rules. These rules generalize across matrix sizes without retraining, demonstrating that autonomous program synthesis can serve as a scalable paradigm for algorithm discovery and the automated design of universal unitary operators. Beyond universal decompositions, the system automatically exploits matrix structure to reduce the interferometer count below the universal theoretical bound. For instance, for Householder matrices, it discovers a dimension-independent rule that requires only $2N-3$ MZIs. This achieves linear, rather than quadratic, scaling and generalizes to arbitrary $N$ without retraining. For matrices obtained from the singular value decomposition of sparse matrices, reductions generally increase with sparsity, reaching up to 38% fewer MZIs than the universal theoretical bound $N(N-1)/2$ at 95% sparsity. These MZI reductions translate directly into practical hardware benefits for scalable photonic implementations. Taken together, the system functions as a single unified engine that discovers both universal decomposition rules and matrix-specific optimizations, without being provided with the structural or analytical properties of the input matrices.

Self-injection locking enables integrated soliton microcombs with turnkey initiation and improved coherence, but it also pins the pump close to resonance, limiting the access to large detuning for broader combs. Here, we use an auxiliary resonator to dynamically hybridize the pump mode, enabling adiabatic access to a far-detuned soliton regime while preserving linewidth narrowing. In a 25-GHz soliton microcomb, the 3-dB bandwidth increases from 17.1 to 26.8 nm, with an added control degree of freedom for near-orthogonal frequency tuning. These results reveal a pathway to broader integrated soliton microcombs beyond the turnkey limit.

We present evidence of the dynamical hysteretic nature of dissipation in unsteady turbulent flows. Wind tunnel experiments and direct numerical simulations in oscillating flows show that, at stationary mean Reynolds number, the dissipation constant is larger for decelerating flows. Consequently, a periodic behavior of the flow produces a hysteresis cycle, whose area scales with a parameter combining the Strouhal number and the relative amplitude of the forcing. This phenomenon can be explained and quantified through the influence of the unsteady term in the Kármán-Howarth equation, with implications for a wide range of out-of-equilibrium systems.

Evidence for a new type of superfluid phase in second-layer ${}^4\mathrm{He}$ on graphite has been obtained from simultaneous measurements of torsional-oscillator response and heat capacity on exactly the same sample down to 30 mK, which resolve substrate-related uncertainties in the previous studies. The new phase hosts both superfluidity and enhanced viscoelasticity relative to the low-density quantum liquid, and is stable over a finite interval of ${}^4\mathrm{He}$ areal density, strongly supporting the proposed “superfluid liquid-crystal” hypothesis. A random-Josephson-network analysis shows that the widely reported log-$T$ dependence of the superfluid density is likely due to substrate imperfections.