Recent experiments reveal increasing detail about the so-called slow Arrhenius process (SAP), which leads to molecular relaxation in glassy systems. The SAP operates over a temperature range that spans melt and glassy states and acts alongside the familiar $\alpha$-relaxation. In this Letter, we propose a mechanistic picture for SAP relaxation wherein local amorphous packing is reshaped by molecular movements that are small in comparison to those in the $\alpha$-modes. Our approach, the collective small displacements (CSD) model, captures a number of experimentally observed SAP characteristics, including its connection to rheology and shear flow. Using a statistical mechanics-based equation of state to obtain nonbonded segmental interaction energies, the CSD model predicts the SAP’s activation energies a priori, based solely on thermodynamic analysis of material properties. The other parameters are all shown to be reasonably material-independent, which means that the model is able to predict SAP relaxation rates and SAP-driven equilibration rates (e.g., adsorption) without using any data on the SAP at all.

In recent years, surface acoustic waves (SAWs) have emerged as a novel technique for generating quasiparticle transport and band modulation in condensed matter systems. SAWs interact with adjacent materials through piezoelectric and strain fields, dragging carriers in the direction of wave propagation. Most studies on the acoustoelectric effect have focused on the collective directional motion of carriers, which generates a steady electric potential difference, while the oscillating component from dynamic spatial charge modulation has remained challenging to probe. In this Letter, we report the coherent detection of the oscillating acoustoelectric effect in graphene. This is achieved through the coherent rectification of spatial-temporal charge oscillation with electromagnetic waves emitted by interdigital transducers. We systematically investigate the frequency and gate dependence of rectified signals and quantitatively probe the carrier redistribution dynamics driven by SAWs. The observation of the oscillating acoustoelectric effect provides direct access to the dynamic spatial charge modulation induced by SAWs through transport experiments.

The lifetime of superconducting qubits is limited by dielectric loss, and a major source of dielectric loss is the native oxide present at the surface of the superconducting metal. Specifically, tantalum-based superconducting qubits have been demonstrated with record lifetimes, but a major source of loss is the presence of two-level systems in the surface tantalum oxide. Here, we demonstrate a strategy for avoiding oxide formation by encapsulating the tantalum with noble metals that do not form native oxide. By depositing a few nanometers of Au or AuPd alloy before breaking vacuum, we completely suppress tantalum oxide formation. Microwave loss measurements of superconducting resonators reveal that the noble metal is proximitized, with a superconducting gap over 80% of the bare tantalum at thicknesses where the oxide is fully suppressed. Our findings suggest that losses in resonators fabricated by subtractive etching are dominated by oxides on the sidewalls, pointing to total surface encapsulation by additive fabrication as a promising strategy for eliminating surface oxide two-level system loss in superconducting qubits.

Bound states in the continuum are presently demonstrated in all-dielectric, metasurface-based cavities of circularly cylindrical shapes. While their cross-sectional sizes may be arbitrary, emphasis is put on the much-needed excitation of these intriguing states in subwavelength cavities. The employed metasurfaces are characterized by effective electric and magnetic surface impedances, allowing for a swift analytical analysis of the underlying problem. The inclusion of magnetic responses, in addition to the electric one, enhances the versatility of the proposed cavities, significantly extending their application, particularly in optical contexts where magnetism is absent. To demonstrate the potential of the proposed method, an all-dielectric metasurface composed of appropriately arranged silicon particles is designed and investigated in the optical frequency range, resulting in a quality factor of $\sim 1.7\times {10}^4$.

We present a unified description of transport in normal and superconducting metals in the presence of generic spin-orbit coupling (SOC). The structure of the quantum kinetic theory in the diffusive regime is determined by a set of fundamental constraints—charge conjugation symmetry, the causality principle, and the crystal symmetry of a material. These symmetries uniquely fix the action of the Keldysh nonlinear $\sigma$ model (NLSM), which at the saddle point yields the quantum kinetic Usadel-type equation, the equation that describes the main transport features of a system. Our phenomenological approach is reminiscent of the Ginzburg-Landau theory but is valid for superconductors in the whole temperature range, describes the diffusive transport in the normal state, and naturally captures the effects of superconducting fluctuations. As an application, we derive the NLSM and the corresponding quantum transport equations, which include all effects of spin-orbit coupling, allowed by the crystal symmetry, for example, the spin Hall, spin current swapping, or spin-galvanic effects. Our approach can be extended to derive transport equations in systems with broken time reversal symmetry, as well as to the description of hybrid interfaces, where the spin-charge interconversion can be enhanced due to strong interfacial SOC.

We test the fluctuation-dissipation relation (FDR) in spin ice materials ${\mathrm{Dy}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$ and ${\mathrm{Ho}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$ by measuring both the magnetic noise and the out-of-phase part of the susceptibility and comparing their ratio. We show that it is satisfied at temperatures well into the nonergodic region below 600 mK, indicating local equilibrium. In both materials, below 400 mK, low frequency violations develop, showing an excess of noise as in spin glasses, with a frequency threshold of 0.1 Hz. New relaxation pathways and aging properties are unveiled in this frequency range in the ac susceptibility. The FDR remains valid at higher frequencies down to 150 mK.

Using equilibrium fluctuations to understand the response of a physical system to an externally imposed perturbation is the basis for linear response theory, which is widely used to interpret experiments and shed light on microscopic dynamics. For nonequilibrium systems, perturbations cannot be interpreted simply by monitoring fluctuations in a conjugate observable and general response results rely on path ensemble averaging. These techniques do not apply to perturbations that affect the diffusion tensor in a stochastic system. Here, we introduce an “effective” physical process that represents the diffusion perturbed dynamics and enables accurate calculations of responses to a change in the diffusion. Interestingly, the effective dynamics contain an additional drift involving the instantaneous “score” of the system, and we leverage score matching algorithms to carry out nonequilibrium response calculations on systems for which the exact stationary distribution is unknown.

In the relentless pursuit of quantum computational advantage, we present a significant advancement with the development of Zuchongzhi 3.0. This superconducting quantum computer prototype, comprising 105 qubits, achieves high operational fidelities, with single-qubit gates, two-qubit gates, and readout fidelity at 99.90%, 99.62%, and 99.13%, respectively. Our experiments with an 83-qubit, 32-cycle random circuit sampling on the Zuchongzhi 3.0 highlight its superior performance, achieving $1\times {10}^6$ samples in just a few hundred seconds. This task is estimated to be infeasible on the most powerful classical supercomputers, Frontier, which would require approximately $5.9\times {10}^9\mathrm{yr}$ to replicate the task. This leap in processing power places the classical simulation cost 6 orders of magnitude beyond Google’s SYC-67 and SYC-70 experiments [Morvan et al., Nature 634, 328 (2024)], firmly establishing a new benchmark in quantum computational advantage. Our work not only advances the frontiers of quantum computing but also lays the groundwork for a new era where quantum processors play an essential role in tackling sophisticated real-world challenges.

When two particles are spin entangled, one may exhibit behavior that suggests its spin can nonlocally influence the spin of the other. This implies that the energy of the latter particle can be altered by a nonlocal quantum correlation, without enabling any form of superluminal communication. This energy alteration, however, remains to be experimentally testified. To test this phenomenon, we construct an incomplete Mach-Zehnder interferometer utilizing two quantum memories. The Stokes photon generated by the quantum memories serves as the first particle, while the atomic excitation stored within the memories acts as the second particle. Our results demonstrate that if the de Broglie–Bohm interpretation is realistic, the trajectory of the Stokes photon can be nonlocally influenced by a slight probe of the atomic excitation. Conversely, the position of the atomic excitation, as well as the energy $\hslash {\omega }_{\mathrm{hf}}$ it carries, can also be nonlocally altered by controlling the Stokes photon. These findings underscore the continued relevance of nonlocality in hidden variable theories, consistent with Bell’s theorem and recent experimental validations, while making clear that such phenomena do not violate the principles of relativity.

Opacity model differences with Fe opacity measurements at high temperature ($\mathrm{T}>180\mathrm{eV}$) and high electron density ($n_e>3\times {10}^{22}{\mathrm{cm}}^{-3}$) at nearly solar interior conditions have remained unresolved [Bailey et al., Nature 517, 56 (2015) and Nagayama et al., Phys. Rev. Lett. 122, 235001 (2019)]. Systematic errors from temporal gradients are one hypothesis for the discrepancy. Past data recorded on x-ray film provided spectral measurements over a time determined by the 2.8-ns backlighter duration. Here, we present the first measurements of opacity sample temporal evolution using novel hCMOS ultrafast x-ray camera technology. The measured conditions, measured backlighter time history, and modeled opacities are used to show that temporal gradients do not resolve the model-data discrepancy. The methods demonstrated provide potential advantages, including opacities at more extreme conditions, spectral line shift measurements, and improved measurements at other facilities.

The ${\mathrm{\Xi }}_b^{0(-)}\to {\mathrm{\Xi }}_c(3055{)}^{+(0)}(\to D^{+(0)}\mathrm{\Lambda }){\pi }^{-}$ decay chains are observed, and the spin-parity of ${\mathrm{\Xi }}_c(3055{)}^{+(0)}$ baryons is determined for the first time. The measurement is performed using proton-proton collision data at a center-of-mass energy of $\sqrt{s}=13\mathrm{TeV}$, corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$, recorded by the LHCb experiment between 2016 and 2018. The spin-parity of the ${\mathrm{\Xi }}_c(3055{)}^{+(0)}$ baryons is determined to be $3/2^{+}$ with a significance of more than $6.5\sigma$ ($3.5\sigma$) compared to all other tested hypotheses. The up-down asymmetries of the ${\mathrm{\Xi }}_b^{0(-)}\to {\mathrm{\Xi }}_c(3055{)}^{+(0)}{\pi }^{-}$ transitions are measured to be $-0.92\pm 0.10\pm 0.05$ ($-0.92\pm 0.16\pm 0.22$), consistent with maximal parity violation, where the first uncertainty is statistical and the second is systematic. These results support the hypothesis that the ${\mathrm{\Xi }}_c(3055{)}^{+(0)}$ baryons correspond to the first $D$-wave $\lambda$-mode excitation of the ${\mathrm{\Xi }}_c$ flavor triplet.

We report on the imaging of the in situ spatial distribution of deterministically prepared single-atom wave packets as they expand in a plane, finding excellent agreement with the scaling dynamics predicted by the Schrödinger equation. Our measurement provides a direct and quantitative observation of the textbook free expansion of a one-particle Gaussian wave packet, which we believe has no equivalent in the existing literature. Second, we utilize these expanding wave packets as a benchmark to develop a protocol for the controlled projection of a spatially extended wave function from continuous space onto the sites of a deep optical lattice and subsequent single-atom imaging using quantum gas microscopy techniques. By probing the square modulus of the wave function for various lattice ramp-up times, we show how to obtain a near-perfect projection onto lattice sites. Establishing this protocol represents a crucial prerequisite to the realization of a quantum gas microscope for continuum physics. The method demonstrated here for imaging a wave packet whose initial extent greatly exceeds the pinning lattice spacing, is designed to be applicable to the many-body wave function of interacting systems in continuous space, promising a direct access to their microscopic properties, including spatial correlation functions up to high order and large distances.

Beams are fundamental objects in solid mechanics, displaying flexural and torsional modes in three dimensions, and support important applications across all fields of engineering. Here, we introduce Maxwell lattice topological mechanics to beams and present a Maxwell beam model that supports topological floppy flexural modes, localized exclusively at one of its ends. We introduce a modified topological index for this Maxwell beam which lacks a complete band gap, and establish a relation between Maxwell topological polarization and frozen evanescent phonons, shedding new light on the bulk origin of the topological localization. The floppy eigenmodes and their exceptional robustness against defects are experimentally validated through vibration measurements on 3D laser-printed samples at kHz frequencies. This study opens new avenues in fields from mechanical and civil engineering to robotics by introducing topologically polarized mechanics in slender structures.

We present a scheme for speeding up quantum measurement. The scheme builds on previous protocols that entangle the system to be measured with ancillary systems. In the idealized situation of perfect entangling operations and no decoherence, it gives an exact space-time trade-off meaning the readout speed increases linearly with the number of ancilla. We verify this scheme is robust against experimental imperfections through numerical modeling of gate noise and readout errors, and under certain circumstances our scheme can even lead to better than linear improvement in the speed of measurement with the number of systems measured. This hardware-agnostic approach is broadly applicable to a range of quantum technology platforms and offers a route to accelerate midcircuit measurement as required for effective quantum error correction.

AMoRE searches for the neutrinoless double beta decay using 100 kg of enriched ${}^{100}\mathrm{Mo}$. Scintillating molybdate crystals coupled with a metallic magnetic calorimeter operate at milli-Kelvin temperatures to measure the energy of electrons emitted in the decay. AMoRE-I is a demonstrator for the full-scale AMoRE, operated at the Yangyang Underground Laboratory for over two years. The exposure was $8.02\mathrm{kg}\mathrm{year}$ (or $3.89{\mathrm{kg}}_{{}^{100}\mathrm{Mo}}\mathrm{year}$), and the total background rate near the $Q$ value was $0.025\pm 0.002\mathrm{counts}/\mathrm{keV}/\mathrm{kg}/\mathrm{year}$. We observed no indication of $0\nu \beta \beta$ decay and report a new lower limit of the half-life of ${}^{100}\mathrm{Mo}$ $0\nu \beta \beta$ decay as $T_{1/2}^{0\nu }>2.9\times {10}^{24}\mathrm{yr}$ at 90% confidence level. The effective Majorana mass limit range is $m_{\beta \beta }<(210–610)\mathrm{meV}$ using nuclear matrix elements estimated in the framework of different models, including the recent shell model calculations.

In this Letter, we report on the experimental generation of high energy (10 GeV), ultrashort (femtosecond-duration), ultrahigh current ($\sim 0.1\mathrm{MA}$), petawatt peak power electron beams in a particle accelerator. These extreme beams enable the exploration of a new frontier of high-intensity beam-light and beam-matter interactions broadly relevant across fields ranging from laboratory astrophysics to strong field quantum electrodynamics and ultrafast quantum chemistry. We demonstrate our ability to generate and control the properties of these electron beams by means of a laser-electron beam shaping technique. This experimental demonstration opens the door to on-the-fly customization of extreme beam current profiles for desired experiments and is poised to benefit a broad swath of cross-cutting applications of relativistic electron beams.

We report a search for neutrino oscillations to sterile neutrinos under a model with three active and one sterile neutrinos ($3+1$ model). This analysis uses the NOvA detectors exposed to the NuMI beam, running in neutrino mode. The data exposure, $13.6\times {10}^{20}$ protons on target, doubles that previously analyzed by NOvA, and the analysis is the first to use ${\nu }_{\mu }$ charged-current interactions in conjunction with neutral-current interactions. Neutrino samples in the near and far detectors are fitted simultaneously, enabling the search to be carried out over a $\mathrm{\Delta }{m}_{41}^2$ range extending 2 (3) orders of magnitude above (below) $1{\mathrm{eV}}^2$. NOvA finds no evidence for active-to-sterile neutrino oscillations under the $3+1$ model at 90% confidence level. New limits are reported in multiple regions of parameter space, excluding some regions currently allowed by IceCube at 90% confidence level. We additionally set the most stringent limits for anomalous ${\nu }_{\tau }$ appearance for $\mathrm{\Delta }{m}_{41}^2\le 3{\mathrm{eV}}^2$.

We describe a magnetic relation in analogy to the well-known dielectric Lyddane-Sachs-Teller relation [R. H. Lyddane et al., Phys. Rev. 59, 673 (1941)]. This magnetic relation follows directly from the model equations for nuclear induction due to fast oscillating electromagnetic fields [F. Bloch, Phys. Rev. 70, 460 (1946)] and relates the static permeability with the product over all ratios of antiresonance and resonance frequencies associated with all magnetic excitations within a given specimen. The magnetic relation differs significantly from its dielectric analog where the static properties are related to ratios of the squares of resonance frequencies. We demonstrate the validity of the magnetic Lyddane-Sachs-Teller relation using optical magnetization data from terahertz electron magnetic resonance spectroscopic ellipsometry measurements in the presence of an external magnetic field on an iron-doped semiconductor crystal of gallium nitride.

We investigated turbulence in 2D atomic Bose-Einstein condensates (BECs) using a minimally destructive, impurity injection technique analogous to particle image velocimetry in conventional fluids. Our approach transfers small regions of the BEC into a different hyperfine state and tracks their displacement, ultimately yielding the velocity field. This allows us to quantify turbulence in the same way as is conventional in fluid dynamics in terms of velocity-velocity correlation functions, called velocity structure functions, that obey Kolmogorov scaling laws. Furthermore, the velocity increments show a clear fat-tail non-Gaussian distribution that results from intermittency corrections to the initial “K41” Kolmogorov theory. Our observations are fully consistent with the later “KO62” description. These results are validated by a 2D dissipative Gross-Pitaevskii simulation.

We report the formation of fcc and distorted hcp iron-helium compounds with $x$ in ${\mathrm{FeHe}}_x$ up to 0.13 and 0.48, respectively, based on experiments at 5–54 GPa and $\sim 1000–2820\mathrm{K}$. Upon releasing pressure under room temperature, these fcc and distorted hcp ${\mathrm{FeHe}}_x$ were still observed by XRD and SIMS measurements. Our first-principles calculations indicate that fcc and hcp ${\mathrm{FeHe}}_x$, with helium atoms occupying the tetrahedral and trigonal-planar interstitial sites (instead of the octahedral sites), are dynamically stable throughout 0–50 GPa. These results support that the Earth’s core can be a large reservoir of primordial ${}^3\mathrm{He}$.