We introduce a high-order dynamical decoupling (DD) scheme for arbitrary bounded system-bath interactions in the weak-coupling regime. Given any decoupling group $\mathcal{G}$ that averages the interaction to zero, our construction guarantees the existence of pulse sequences with at most $(|\mathcal{G}|-1)K$ pulses, while canceling all error terms linear in the system-bath coupling strength up to order $K$ in the total evolution time. As a corollary, for an $n$-qubit system with $k$-local system-bath interactions, we obtain an $\mathcal{O}(n^{k-1}K)$-pulse sequence, a significant improvement over existing schemes with $\mathcal{O}(\exp (n))$ pulses [for $k=\mathcal{O}(1)$]. The construction is obtained via a mapping to the continuous necklace-splitting problem, which asks how to cut a multicolored interval into pieces that give each party the same share of every color. We provide explicit pulse sequences for suppressing general single-qubit decoherence, prove that the pulse count is asymptotically optimal, and verify the predicted error scaling in numerical simulations. For the same number of pulses, we observe that our sequences outperform the state-of-the-art quadratic DD in the weak-coupling regime. We also construct explicit high-order sequences for suppressing representative 2-local noise models. Finally, the same construction extends to suppress slow, time-dependent classical noise and to filter-function design.

The quantum cryptographic conferencing (QCC) protocol, which distributes identical secure keys to user groups, is a crucial component of the quantum network. Previous experimental works have implemented the measurement-device-independent (MDI) QCC, of which the key rate in an $N$-user network scales as $R\sim O({\eta }^N)$. Building on the MDI QCC protocol, the asynchronous MDI QCC protocol theoretically integrates the mode-pairing scheme into QCC, significantly boosting the key rate to $R\sim O(\eta )$ in the ideal case, which is independent of the number of users, thus demonstrating greater application potential. Experimentally, in this Letter, we implement the three-user asynchronous MDI QCC network without phase locking by adopting the fast Fourier transform-based frequency difference estimation and the phase drift compensation technique. Finally, we achieve a key rate of about $4.470\times {10}^{-9}\mathrm{bits}$ per pulse under a maximum overall loss of about 59.6 dB. This Letter provides a scalable solution for the development of large-scale quantum communication networks in the future.

We report on a search for sub-GeV dark matter upscattered via the solar reflection mechanism in the heavy mediator scenario. Under the standard halo model, keV–MeV dark matter produces nuclear recoils with energies below the detection threshold of liquid xenon time projection chambers. We enhance sensitivity to low-mass dark matter (DM) by considering dark matter–electron scattering, employing dedicated event selections to reduce the detection threshold and exploiting the additional kinetic energy imparted to the dark matter particle by solar upscattering. Using XENON1T ionization-only and XENONnT low-energy electronic recoil datasets, we exclude previously unconstrained DM-electron scattering cross section for masses between 4.6 and $20\mathrm{keV}/c^2$ and between 0.2 and $2\mathrm{MeV}/c^2$, reaching a minimum of $3.41\times {10}^{-39}{\mathrm{cm}}^2$ for a mass of $0.3\mathrm{MeV}/c^2$ at 90% confidence level.

This Letter presents a measurement of prompt charged-particle production in proton-oxygen interactions at $\sqrt{s_{\mathrm{NN}}}=9.62\mathrm{TeV}$ center-of-mass energy with the ATLAS detector, corresponding to $634\mu {\mathrm{b}}^{-1}$ of integrated luminosity. A total of $246\times {10}^6$ selected events have at least one track with transverse momentum $p_{\mathrm{T}}>500\mathrm{MeV}$ and pseudorapidity $|\eta |<2.5$. The measured fiducial proton-oxygen cross section is ${\sigma }_{\mathrm{fid}.}^{p\mathrm{O}}=396\pm 6(\exp .)\pm 9(\mathrm{lumi}.)\mathrm{mb}$ and the extrapolated inelastic proton-air cross section is ${\sigma }_{\mathrm{inel}.}^{p+\mathrm{air}}=406\pm 6(\exp .)\pm 9(\mathrm{lumi}.)\pm 28(\mathrm{th}.)\mathrm{mb}$. Measurements of charged-particle multiplicity, $p_{\mathrm{T}}$, and $\eta$ distributions are an order-of-magnitude more precise than differences between hadronic-interaction models. These results enable improved modeling of cosmic-ray air showers, which is important for astroparticle physics.

The magnetic dynamics at the nanoscale interface of amorphous insulators sit at the intersection of advancing ultrasensitive quantum sensing and understanding condensed matter physics. While noble-gas spin relaxation offers a powerful approach to probe these interfaces, it has long been restricted to probing bulk paramagnetic backgrounds due to the deep penetration depths of traditional dipolar probes. In this Letter, we report the observation of nanotesla-level magnetic hysteresis and thermally activated relaxation growth in aluminosilicate glass cells using ${}^{21}\mathrm{Ne}$ as a quadrupolar-enhanced quantum probe. The strong coupling between the nuclear electric quadrupole moment and the surface electric field gradient compresses the effective spin sampling depth to the nanometer scale [$\sim \mathcal{O}(1)\mathrm{nm}$]. By coupling Jiles-Atherton hysteresis dynamics with Cates diffusion and accounting for gas-phase thermal line broadening, we obtain a cross-cell average apparent activation energy of $⟨E_{\mathrm{act}}⟩\approx 49.7\mathrm{kJ}/\mathrm{mol}$ within the present relaxation model. The pronounced field-history dependence of the relaxation is consistent with localized magnetic inhomogeneity at the glass interface. The proposed methodology provides an in situ, nondestructive, depth-selective probe of magnetic behavior at otherwise inaccessible amorphous glass interfaces, with potential utility for identifying wall-related relaxation in ultrasensitive comagnetometers.

We report the experimental observation of motion-induced directionality in collective atomic emission within a hollow-core waveguide, establishing a general principle: directional interactions can emerge from collective phase engineering alone. Remarkably, neither single-emitter asymmetry nor any asymmetry in the geometric arrangement of the system is required—both the atom-field coupling and the spontaneous emission are fully isotropic in our system. Instead, Raman-induced effective two-level emitters with spatially oscillating transition dipole phases and atomic motion give rise to controllable directionality, reaching values up to 0.89(1). We study the correlations of the superfluorescent bursts close to and well above the threshold to collective emission; we find thermal statistics below and a buildup of coherence above it. Numerical simulations based on the truncated Wigner approximation for spins yield good agreement. Additionally we present a simple model based on position uncertainty capable of reproducing the observed directionality. Our results open a new route to directional interactions in nonchiral systems, with direct implications for the design of directional metamaterials and photonic structures built from isotropic constituents.

Orbit-resolved paired resonances, sharing the same orbital period but arising from distinct phase-space structures, provide a direct probe of wave localization in chaotic microcavities. Here, we report the orbit-resolved visualization of paired resonances in a chaotic optical microcavity using a multiphoton fluorescence scheme. The high-$Q$ island modes on stable periodic orbits and scarlike modes by partial-barrier localization in the chaotic sea are identified across multiple orbital periods. Guided by the orbit-resolved modal morphologies, phase-space selective excitation is demonstrated by tailoring the waveguide injection. Furthermore, tunneling-mediated modal hybridization between classically disjoint orbits is revealed through directly visualized superposed patterns and anticrossing spectra. Our results establish a direct link between photon dynamics and modal structure, opening a route to exploring nonlinear physics in wave-chaotic systems.

Using theory and numerical simulations, here we describe the early stages of the impact with a velocity $V$ of a drop of radius $R_d$ of a low viscosity liquid such as water against a layer of generic thickness $H$ of the same liquid. Our predictions for the initial velocity $V_t\gg V$ and the diameter $H_t\ll R_d$ of the toroidal rim bordering the edge of the thin lamella which is ejected radially outwards after the impact, are in fair agreement with both the numerical results and also with the experimental measurements reported by Zhang et al. [J. Fluid Mech. 690, 5 (2012)]. Consequently, the present findings can be employed, for instance, to predict the initial diameters and velocities of the fastest tiny droplets which are ejected right after a rain drop falls on a liquid pool, an ubiquitous phenomenon with implications in the dispersal of contaminants and in the generation of aerosols and of ice condensation nuclei.

The quantum metric encodes the geometric structure of Bloch wave functions and governs a wide range of physical responses. Its Brillouin-zone integral, the quantum weight, appears in the structure factor and provides lower bounds on observables such as the optical gap and dielectric constant. In symmetry-protected topological (SPT) phases, the nontrivial band topology imposes a lower bound on the quantum weight and constraints on the observables. Here, we generalize the topological bound on quantum geometry to encompass systems beyond the SPT phases. We show that topological invariants defined via the projected spectrum lower-bound the quantum weight with a symmetry-breaking correction to the quantum metric. Our proposed bound holds even when the underlying symmetries are broken, and it would be amenable to experimental verification via the optical conductivity sum rule under external fields. We illustrate our theory by adding a nonzero spin-orbit coupling term to a spin Chern insulator model, where we show that our proposed bound applies even though the conventional topological bound does not hold.

Magnetic skyrmions (MSks) and optical skyrmions (OSks) embody topology in matter and in light, respectively. Here we investigate the interaction between a single MSk and an OSk beam. Three distinct nonlinear dynamical modes are identified: rotation, skipping, and trochoidal motion. By decomposing the optical driving force into gradient, orbital-angular-momentum, and spin-angular-momentum contributions, we clarify their respective roles of radial confinement, azimuthal drift, and precessional modulation. The skipping motion arises from the azimuthal asymmetry of the OSk beam and exhibits spatial selectivity originating from the magnetization-polarization coupling between the MSk and OSk. In three dimensions, the coupling acquires a propagation-dependent phase dominated by the differential Gouy phase, which yields $z$-asymmetric skipping trajectories. These results bridge topological particles and topological fields within a unified framework, offering helicity-selective and phase-programmable routes to optomagnonic control.

Compensated magnets are of increasing interest for both fundamental research and applications, with their net-zero magnetization leading to ultrafast dynamics and robust order. To understand and control this order, nanoscale mapping of local domain structures is necessary. One of the main routes to mapping antiferromagnetic order is x-ray magnetic linear dichroism (XMLD), which probes the local orientation of the Néel vector. However, XMLD imaging typically suffers from weak contrast and has mainly been limited to surface-sensitive techniques. Here, we harness coherent diffractive imaging to map the complex XMLD spectroscopically, and identify the phase linear dichroism as a high-contrast, high-resolution mechanism for imaging magnetic order. By applying x-ray spectroptychography to a model sample, we retrieve the full complex XMLD spectrum. Combining this with hierarchical clustering, we resolve the spatial distribution of probed domains by their distinct spectral signatures, providing a robust method for analyzing magnetic configurations with weak signals. Our results show that phase contrast is significantly stronger than the corresponding absorption contrast, offering higher spatial-resolution magnetic imaging. This approach establishes a reliable element- and orbital-sensitive tool for studying compensated magnets.

Excitonic effects dominate absorption and loss spectra in many materials. However, they are hard to access computationally, because of the cost of first-principles calculations and because of the scarce reliability of simple approximations. We overcome both limitations by combining a part of the electron-hole Bethe-Salpeter equation with an effective scalar interaction. The partitioning is motivated by the general form of the electron-hole interaction and it can be applied to all materials. First-principles calculations for prototypical semiconductors and insulators demonstrate a speedup of 1 to 2 orders of magnitude for results close to those where the full interaction matrix is used. The method is systematic and can be converged to the benchmark.

We solve the orientation recovery of a tumbling protein in the gas phase from single-event measurements of the spatial positions of its ions after an x-ray laser-induced explosion. We simulate diffracted x-ray signal and ion dynamics under experimental conditions and compare our method to conventional orientation recovery in single-particle imaging with x-ray free-electron lasers using only diffraction data. We reconstruct 3D diffraction intensities using orientations recovered from the ion signatures and retrieve the electron density with established phase-retrieval algorithms. We test our orientation recovery procedure on 56 proteins ranging from 14 to 52 kDa (1800 to 6500 atoms), achieving an angular error of around $5°$. The resulting 3D electron-density reconstructions are compared to ground-truth volumes simulated at the same nominal resolution and achieve the resolution at the edge of the detector in conditions similar to current single-particle imaging setups. We investigate the reconstruction quality and demonstrate that ion data can be used for reliable orientation recovery of particles in single-particle imaging, achieving orientation on par with or better than currently used recovery techniques. This Letter shows the potential of ion detection for retrieving additional information from the sample fragmentation and boosting single-particle imaging with x-ray lasers in the cases where the diffraction signal is a limiting factor.

The removal of heat generated during computation poses a major challenge for both classical and quantum computation and information processing. In particular, removal of this heat is intrinsically tied to one of the fundamental requirements of quantum computation—the need to reset the system to a pure state before computation. Therefore, efficient cooling is of paramount importance, not only for deepening our understanding of thermodynamics in the quantum regime but also for advancing the development of modern quantum technologies. In this Letter, we devise a cooling task that exploits steerability—a fundamental feature of quantum correlations—to demonstrate a provable quantum thermodynamic advantage over classically correlated scenarios where steerability is absent. We quantify the advantage by the ratio of the amount of heat removed using steerable (quantum) correlations to that obtained with unsteerable (classical) correlations. Specifically, we show that steerable quantum correlations always yield a thermodynamic advantage in a cooling task over their classical counterparts. Remarkably, we further establish that the maximum achievable advantage is directly related to a geometric measure of steerability called steerability robustness. Our results suggest that this thermodynamic advantage can be interpreted as a witness of steerability. Finally, we present examples in which the advantage grows with the dimension of the underlying system.