Long-lived storage of single photons under the form of atomic excitations is at the foundation of long-distance entanglement distribution in quantum networks. To mitigate decoherence effects induced by the environment, rephasing of the hyperfine coherences using microwave pulses have been implemented in a variety of single-emitter and ensemble-based solid-state systems. However, the demonstration of storage of single photons in an absorptive quantum memory including such a spin-rephasing mechanism remains elusive. In this Letter, we show nonclassical storage of telecom-heralded single photons in a ${\mathrm{Pr}}^{3+}:{\mathrm{Y}}_2{\mathrm{SiO}}_5$ rare-earth ion doped crystal quantum memory using the atomic frequency comb spin-wave protocol combined with a XY4 spin-rephasing sequence. Long-lived atomic frequency comb photon echoes are first observed in the classical regime for storage times of up to approximately 3 ms. We then demonstrate nonclassical correlations between heralding photons and stored signal photons generated by a cavity-enhanced parametric photon-pair source for storage times of up to $180\mathrm{\mu }\mathrm{s}$ and with measured cross-correlation values as high as 4.6(4). Together with the capacity of ${\mathrm{Pr}}^{3+}:{\mathrm{Y}}_2{\mathrm{SiO}}_5$ quantum memories to support highly efficient and multiplexed storage, this result represents a significant step toward scalable long-distance quantum repeater links.

For ultrafast magnetization switching devices, critical slowing down in conventional ferromagnets near their Curie temperature constitutes a key challenge that must be overcome. In contrast to this typical behavior, we observe an anomalous acceleration of demagnetization in ${\mathrm{CaRuO}}_3/{\mathrm{SrTiO}}_3$ superlattices, which are moderately correlated weak itinerant ferromagnets. The demagnetization rate increases with rising temperature, pump fluence, and applied magnetic field. To explain these anomalous phenomena, we develop a phenomenological model integrating the three-temperature model with self-consistent renormalization theory. Because the intrinsic gradient magnetism of the superlattice suppresses the typical divergence of specific heat, the conventional thermodynamic bottleneck is bypassed. Our model reveals that this decoupling enables the ultrafast dynamics to be predominantly governed by the spin-fluctuation-driven enhancement of the electron-spin scattering vertex. This Letter demonstrates how spatial inhomogeneity can decouple macroscopic thermodynamic singularities from microscopic scattering processes, offering a new paradigm for manipulating ultrafast spin dynamics in correlated quantum materials. The pronounced sensitivity of the demagnetization rate to external parameters further suggests the potential for designing highly tunable ultrafast spintronic devices that leverage enhanced fluctuations near the magnetic instability.

Compact double neutron star (DNS) systems are unique laboratories for testing gravitational theories and studying DNS mergers. Here we report the properties of a new DNS system, PSR J1856–0039, discovered in the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The pulsar is mildly recycled with a period of 23.4 ms in a compact eccentric orbit ($e=0.106$) with an orbital period of 2.36 hours. By following up FAST observations, we measured the relativistic effects, including the orbital period derivative ${\dot{P}}_{\mathrm{orb}}=-1.284\pm 0.019\times {10}^{-12}\mathrm{s}{\mathrm{s}}^{-1}$, periastron advance $\dot{\omega }=17.5859\pm 0.0007\mathrm{deg}{\mathrm{yr}}^{-1}$, and Einstein delay $\gamma =0.445\pm 0.011\mathrm{ms}$. This DNS system has a low orbital inclination of $i=133\stackrel{\circ }{.}2\pm 1\stackrel{\circ }{.}1$ and the lowest total mass of any known DNS, $M_{\mathrm{tot}}=2.48841\pm 0.00015M_{\odot }$, with a determined pulsar mass of $1.304\pm 0.022M_{\odot }$ and a companion mass of $1.185\pm 0.022M_{\odot }$, one of the lowest neutron-star masses. The observed orbital decay due to gravitational-wave emission ${\dot{P}}_{\mathrm{orb},\mathrm{obs}}^{\mathrm{GW}}$ and the orbital decay predicted by general relativity ${\dot{P}}_{\mathrm{orb},\mathrm{pred}}^{\mathrm{GW}}$ are consistent at a level of ${\dot{P}}_{\mathrm{orb},\mathrm{obs}}^{\mathrm{GW}}/{\dot{P}}_{\mathrm{orb},\mathrm{pred}}^{\mathrm{GW}}=1.009(14)$ (68% confidence). This DNS will merge after 82 Myr and may form a stable neutron star or collapse into a black hole after spin-down. Long-term monitoring could potentially probe the Lense-Thirring precession.

We uncover a dual mechanism by which oxygen defects suppress superconductivity in the bilayer nickelate ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_{7+\delta }$ using density functional theory, dynamical mean-field theory, and functional renormalization group analysis. Apical vacancies and interbilayer interstitials emerge as the dominant low-energy defect species and are further stabilized by orthorhombic domain walls. These two defect classes drive the electronic structure in opposing directions. Vacancy-induced disorder generates local magnetic moments and promotes Anderson localization at moderate concentrations, whereas periodic interstitial ordering yields a coherent but weakly correlated metallic background that fails to support superconductivity. These findings highlight the decisive role of oxygen defects in shaping superconductivity and provide microscopic guidance for improving it through controlled defect engineering.

We show that excitons forming between moiré flat Chern bands possess a substantial electric dipole moment comparable to the moiré lattice parameter times the elementary charge ($\sim {10}^2\mathrm{D}$). At a hole filling factor of 1 in twisted ${\mathrm{MoTe}}_2$, the dipole moment of the lowest-energy exciton branch develops in-plane helical texture in momentum space from the intrinsic Berry curvature of electron and hole. By solving the Bethe-Salpeter equations, we demonstrate that an out-of-plane displacement field induces a Frenkel-to-Wannier exciton transition, accompanied by a reversal of the dipole texture helicity. The giant dipole produces an attractive dipole-dipole interaction channel, suggesting a possible quadrupolar biexciton measurable via two-photon spectroscopy. Our findings establish band topology as a tunable knob to engineer exciton dipole moments and pave the way to manipulate many-body interactions in the terahertz regime.

We report numerical evidence for a wave-turbulent regime in dense suspensions of active phoretic disks with physicochemical hydrodynamic interactions. At low activity, the disks assemble into active Wigner solids, which melt into a hexatic phase with increasing activity. This phase transition in dense suspensions is accompanied by the destruction of standing waves in the solid phase and the onset of turbulent dynamics in the hexatic phase. Unlike canonical active turbulence typically characterized by large-scale advection of self-propelling constituents, our disks remain caged and perform local vibrations. This behavior mirrors the weak turbulence of bending waves in vibrating elastic plates. Moreover, the observed turbulence displays a self-similar, power-law energy spectrum at large wavenumbers, scale-dependent spatial intermittency but weak temporal intermittency, and statistically weak nonlinearity, consistent with reported signatures of wave turbulence. We therefore identify a new wave turbulence regime in active matter’s hexatic phase, which we call active wave turbulence.

The superconducting dome in the $T_c$ versus doping phase diagram, found in cuprates, nickelates, twisted bilayer graphene, and transition metal dichalcogenides, is often considered a signature of unconventional pairing. Identifying the underlying mechanisms of any of these phase diagrams and developing a reliable theoretical understanding of it remains a critical challenge. Here we demonstrate that, in ionic-liquid-gated quasi-2D materials, the disordered ionic potential from the frozen ionic liquid drives the system close to Anderson transition. In this regime, quenched charge fluctuations and reduced screening markedly enhance repulsive Coulomb interactions, suppressing $T_c$ and naturally leading to the formation of a superconducting dome. By integrating a many-body approach including disorder with first-principles calculations, we obtain the phase diagrams and tunneling spectra of gated few-layer transition metal dichalcogenides in robust quantitative agreement with experiments. Our findings establish that disorder-driven enhancement of Coulomb repulsion is a fundamental feature of ionic-liquid-gated quasi-2D materials at high bias.

The commensurate charge-density-wave phase of the prototypical transition metal dichalcogenide $1T\text{−}{\mathrm{TaS}}_2$ is investigated by temperature- and polarization-dependent infrared spectroscopy, revealing distinct charge dynamics parallel and perpendicular to the layers. Supported by density-functional-theory calculations, we show that the in-plane electronic structure in the low-temperature commensurate phase is reconstructed by the $\sqrt{13}\times \sqrt{13}$ distortion of the Ta layers. In contrast, the out-of-plane response is governed by a quasi-one-dimensional, Peierls-like dimerization of the two-dimensional Star of David layers. Our results identify this dimerization as the dominant mechanism of the metal-to-insulator transition in both directions, rather than correlation-driven Mott localization.

Altermagnetism as a new concept in condensed matter physics is currently being thoroughly investigated. Despite the absence of macroscopic magnetization, altermagnets host a hidden spin order whose direct detection remains a challenge. Here, we report on the observation of electric-dipole forbidden optical second-harmonic generation (SHG) in the altermagnet ${\mathrm{CoF}}_2$ with a centrosymmetric lattice and spin order. We demonstrate that below the Néel temperature $T_N=38\mathrm{K}$, the SHG signal is sensitive to the ferro-type magnetic octupole ${\mathcal{O}}^M$, which is the order parameter in the antiferromagnetic phase. By combining polarization-resolved SHG experimental data and a phenomenological symmetry analysis, we show that the altermagnetic spin structure of ${\mathrm{CoF}}_2$ enables a ferroic-octupole-induced electric-quadrupolar nonlinear polarization ${\mathbf{P}}^{2\omega }=\mathrm{i}{ϵ}_0^c{\mathit{\chi }}^{(3)}({\mathcal{O}}^M):{\mathbf{E}}^{\omega }\nabla {\mathbf{E}}^{\omega }$. The temperature dependence of SHG reveals a phase transition at $T_N$, confirming the spin origin of the observed signal. The SHG response is resonantly enhanced by a coherent three-photon process caused by the electronic $d\text{−}d$ transitions of the ${\mathrm{Co}}^{2+}$ ion. Model calculations of SHG polarization rotational anisotropies and temperature dependencies give a reasonable agreement with experimental data, proving the disclosed nonlinear contribution. Our results establish SHG as a novel sensitive tool of ferroic-octupolar spin ordering and highlight the potential of ${\mathrm{CoF}}_2$ and other altermagnets for further nonlinear optical investigations and applications.

Biological systems sense and extract information from fluctuating signals while operating under energetic constraints and limited resolution. We introduce a general chemical model in which a signaling pathway is activated by hidden signals and produces a readout molecule. A sensor, here modeled as an abstract optimization agent, is coupled to the signaling process and can tune the readout production. We propose viable strategies for the sensor to estimate, and eventually balance, information gathering on the hidden process and the associated dissipative cost relying solely on counting statistics of observed trajectories. We show that these strategies can be successfully implemented to adapt the readout production even with finite-time measurements and limited dynamic resolution, and remain effective in the presence of inhibitory regulatory mechanisms. Our Letter provides a plausible mechanism to actively balance information and dissipation, paving the way for an implementable design principle underpinning biological and biochemical adaptation.

Entanglement is a key property of quantum systems. In this Letter the first measurements of quantum entanglement between spins in pairs of $Z$ bosons are reported, using proton-proton collision data from the Large Hadron Collider (LHC) at center-of-mass energies of 13 and 13.6 TeV, recorded with the ATLAS detector. Measurements of angular observables sensitive to $Z{Z}^{*}$ spin-density-matrix elements in the $H\to Z{Z}^{*}\to {\ell }^{+}{\ell }^{-}{\ell }^{+}{\ell }^{-}$ process yield coefficients $C_{2,1,2,-1}=-0.71\pm 0.45$ and $C_{2,2,2,-2}=0.08\pm 0.44$, consistent with their Standard Model predictions. A complementary hypothesis test using the full angular distribution, and relying on several Standard Model assumptions in the decays, provides substantially higher sensitivity to quantum correlations and disfavors the separable-state hypothesis at a significance of 4.7 standard deviations (expected $4.9\sigma$) relative to the entangled Standard Model hypothesis. These results provide strong evidence of quantum entanglement between massive bosons (spin qutrits) at the electroweak scale.

The mechanisms, pathways, and driving force for the classical $B1\text{−}B2$ transitions have long been elusive. Here, we conduct ultrafast x-ray diffraction measurements and systematic atomistic simulations of single-crystal KCl under shock compression and establish a unified model for the $B1\text{−}B2$ transition in KCl. The transition proceeds via resolved-shear-stress-driven slip through two generalized transition pathways, yielding two generalized $B1\text{−}B2$ orientation relationships. Resolved-shear-stress-driven slip is potentially a common mechanism for general $B1\text{−}B2$ transitions.

First-principles predictions of excitation energies and cross sections in inelastic tunneling spectroscopy are challenging, making it difficult to assign experimental features to specific excitations. There is, however, a need for a reliable identification of conductance features. We investigated the spin-$1/2$ molecule cobaltocene on superconducting Pb(110) and employ Yu-Shiba-Rusinov states combined with a superconducting tip to detect a large number of sharp spectral features. From an analysis of the peak heights at both bias voltage polarities along with model calculations and density-functional theory results we identify spin, vibrational, and orbital excitations that coexist within a single conductance spectrum. The peak height asymmetry turns out to be a useful indicator to determine the type of excitation.

Arctic sea ice fluctuates in response to its turbulent environment, leading to dispersion behaviors that are not well understood. We resolve this gap using simulations that model sea ice as a granular medium that responds to stochastic winds. Using only directly measured local environmental and ice properties as inputs, the model quantitatively reproduces the dispersion, velocity distribution, and power spectrum of sea ice observed in the Fram Strait. These transport properties are generic consequences of collisions between floes, which rapidly dissipate the energy injected by wind while shortening the mean free paths of floes. A Boltzmann transport kinetic theory yields further quantitative insight, recovering both the simulations and observations. Our findings connect floe-scale dynamics and local environmental noise to properties of sea ice at climate-relevant scales, while also establishing broader links to stochastically driven dissipative granular systems.

We demonstrate the microwave signatures of individual Abrikosov-vortex penetration events in superconducting microwave resonators. $\lambda /4$ resonators with a narrowed region near the grounded end acting as a vortex trap were fabricated and studied using microwave transmission spectroscopy at millikelvin temperatures. Sharp stepwise drops in resonance frequency are detected as a function of increasing external magnetic field, attributed to the entry of individual Abrikosov vortices in the narrow region. This interpretation is confirmed by nitrogen-vacancy center magnetometry, revealing discrete vortex entry events on increasing field and the absence of such drops in a device with a wider narrowed region. Our results establish a method to investigate and manipulate the states of Abrikosov vortices with microwaves access and readout vortex configurations using magnetic-field sweeps and microwave drive.

Electron vortices are an expected manifestation of viscosity, yet their detection remains challenging. We introduce a nanomechanical paradigm: a vortex in a suspended resonator generates a magnetic moment that, in an in-plane field, drives vibrations via magnetic torque. Using a comparative design with a reference device where vortices are suppressed, we provide unambiguous identification of the circulating flow. We detect ballistic and hydrodynamic vortices and trace their temperature crossover. Our work establishes nanomechanics as a direct force-sensing platform for electron hydrodynamics.

We demonstrate complete, all-optical control over the chirality and ellipticity of high-harmonic generation by manipulating dynamical symmetry with a phase-locked two-color field. This control arises from subcycle symmetry breaking governed by the quantum geometry of laser field-driven electronic states, which modifies the polarization selection rules. Specifically, by engineering the spectral phase between orthogonal harmonic components encoding both the transition dipole phase and interband Berry phase, we realize deterministic polarization control of even-order harmonics. When applied to representative materials such as ${\mathrm{Bi}}_2{\mathrm{Se}}_3$, BiTeI, and GaSe, this scheme reveals polarization responses that vary qualitatively with material-specific electronic structure, underscoring the profound influence of quantum geometry. The polarization manipulation is dictated by the driving field parameters, allowing full coverage of the Poincaré sphere when combined with crystal rotation.

By generalizing a class of models recently introduced to account for protracted transients in biological systems, we identify a novel mechanism for hyperuniformity. In this model, competition of individuals over a shared resource serves as feedback that can asymptotically guide the population toward a critical steady state with a divergent individual lifetime. We show that, in its spatially extended form, this many-body model exhibits hyperuniform density fluctuations. Through explicit coarse-graining, we develop a hydrodynamic theory that conforms closely with the results of stochastic simulations. Unlike previous models for nonequilibrium hyperuniform states, our model does not exhibit conservation laws, even in the asymptotic regime. Instead, hyperuniformity arises from the divergence of the range of the resource-mediated interactions. These findings may find applications in engineering, cellular population dynamics, and ecology.

Using synchrotron x-ray diffraction in laser-heated diamond anvil cells, we report the observation of a hexagonal close-packed (hcp) phase of water ice at high pressure and temperature conditions. Above 200 GPa and 1800 K, the hcp phase becomes dominant upon entering the superionic regime, as evidenced by anomalous thermal expansion. Observations are consistent with the hcp phase becoming thermodynamically more stable than the face-centered cubic (fcc) phase via a martensitic transition extending across the 130–200 GPa pressure range, within the superionic regime. Hcp ice is also observed to emerge from stacking disorder developing within the fcc oxygen lattice upon cooling, during its reversion to the body-centered cubic phase. The presence of an fcc-hcp martensitic transition in the superionic regime of warm dense ice may have implications for planetary models of Uranus and Neptune.