The ability to determine precisely the separation of two frequencies is fundamental to spectroscopy, yet the resolution limit poses a critical challenge: distinguishing two incoherent signals becomes impossible when their frequencies are sufficiently close. Here, we demonstrate a simple and powerful approach, dubbed superresolution quantum sensing, which experimentally resolves two nearly identical incoherent signals using a solid-state spin quantum sensor. By carefully choosing interrogation times that satisfy the superresolution condition, we eliminate quantum projection noise, overcoming the vanishing distinguishability of signals with near-identical frequencies. This leads to improved resolution, which scales as $t^{-2}$ in comparison to the standard $t^{-1}$ scaling. Together with a greatly reduced classical readout noise assisted by a nuclear spin, we are able to achieve sub-kHz resolution with a signal detection time of 80 $\mathrm{\mu }\mathrm{s}$. Our results highlight the potential of quantum sensing to overcome conventional frequency resolution limitations, with broad implications for precision measurements.

The multimode acoustic gravitational wave experiment (MAGE) is a high-frequency gravitational wave detection experiment featuring cryogenic quartz bulk acoustic wave resonators operating as sensitive strain antennas in the MHz regime. After 61 days of noncontinuous data collection, we present bounds on the observable merger rate density of primordial black hole binary systems of chirp mass $1.2\times {10}^{-4}{M}_{\odot }<\mathcal{M}<1.7\times {10}^{-9}{M}_{\odot }$. The maximum achieved limit on the merger rate density is $\mathcal{R}<1.3\times {10}^{18}{\mathrm{kpc}}^{-3}{\mathrm{yr}}^{-1}$, which corresponds to constraining yearly mergers to a distance of reach on the order of the Solar System, or $1.0\times {10}^{-6}\mathrm{kpc}$ during the observational period. In addition, we exclude significantly rare and strong events similar to those observed in previous predecessor experiments as nongravitational background signals, utilising coincident analysis between multiple detectors.

The MicroBooNE experiment is an 85 tonne active mass liquid argon time projection chamber neutrino detector exposed to the on-axis Booster Neutrino Beam at Fermilab. One of MicroBooNE’s physics goals is the precise measurement of neutrino interactions on argon in the 1 GeV energy regime. Building on the capabilities of the MicroBooNE detector, this analysis identifies $K^{+}$ mesons, a key signature for the study of strange particle production in neutrino interactions. This measurement is furthermore valuable for background estimation for future nucleon decay searches and for improved reconstruction and particle identification capabilities in experiments such as the Deep Underground Neutrino Experiment. In this Letter, we present the first-ever measurement of a flux-integrated cross section for charged-current muon neutrino induced $K^{+}$ production on argon nuclei, determined to be $7.93\pm 3.22(\mathrm{stat})\pm 2.83(\mathrm{syst})\times {10}^{-42}{\mathrm{cm}}^2/\mathrm{nucleon}$ based on an analysis of $6.88\times {10}^{20}$ protons on target. This result was found to be consistent with model predictions from different neutrino event generators within the reported uncertainties.

Shape coexistence, a collective manifestation of nuclear structure, emerges from the underlying single-particle dynamics and is prominently observed in the region below ${}^{68}\mathrm{Ni}$. Theoretical studies have emphasized the key role of the $\nu d_{5/2}$ orbital, the quadrupole partner of $\nu g_{9/2}$, in driving deformation. However, experimental constraints on the location and properties of neutron orbitals in neutron-rich isotopes in this region remain scarce. In this Letter, the single-particle structure of ${}^{69}\mathrm{Ni}$ was investigated via the ${}^{68}\mathrm{Ni}(d,p)$ reaction in inverse kinematics, performed at the ISOLDE Solenoidal Spectrometer at CERN. Several new excited states were observed, and comparisons with adiabatic distorted wave approximation (ADWA) calculations enabled $\ell$-value assignments for the most strongly populated states. In particular, a state at 2.56 MeV is interpreted as the dominant fragment of the $\nu d_{5/2}$ strength. The experimental findings are well reproduced by Large-Scale Shell Model calculations using a modified LNPS interaction with an increased $\nu g_{9/2}–\nu d_{5/2}$ energy gap. These results provide new insight into the structure of ${}^{69}\mathrm{Ni}$ and underscore the crucial role of the $\nu d_{5/2}$ orbital in the onset of collectivity at the $N=40$ island of inversion.

Dispersive readout, the standard method for measuring superconducting qubits, is limited by multiphoton qubit-resonator processes arising even at moderate drive powers. These processes degrade performance, causing dispersive readout to lag behind single- and two-qubit gates in both speed and fidelity. In this Letter, we propose a novel readout method, termed junction readout. Junction readout leverages the nonperturbative cross-Kerr interaction resulting from coupling a qubit and a resonator via a Josephson junction. Furthermore, by adding a capacitive coupling in parallel to the junction, Purcell decay induced by the exchange coupling can be suppressed. We also show that junction readout is more robust against deleterious multiphoton processes, and offers greater flexibility for resonator frequency allocation. Crucially, junction readout achieves superior performance compared to dispersive readout while maintaining similar hardware overhead. Numerical simulations show that junction readout can achieve fidelity exceeding 99.99% in under 30 ns of integration time, making it a promising alternative for superconducting qubit readout with current hardware.

Van der Waals layered materials offer unprecedented opportunities to tune electronic properties by controlling, for instance, the number of layers or their mutual twist angle. However, the translational degree of freedom has not been given proportionate attention. Within the wide family of transition metal dichalcogenides, the commensurate charge density wave (CCDW) phase of $1T\text{−}{\mathrm{TaSe}}_2$ is predicted to host several quantum states ranging from 1D metal to 3D insulator depending on the lateral stacking. By means of angle-resolved photoemission spectroscopy with micrometer spatial resolution, we studied the charge-ordered $1T\text{−}{\mathrm{TaSe}}_2$, revealing the coexistence of metallic and insulating surface domains. Our investigation clarifies that metallicity is due to a specific lateral sliding of the CCDW layers, while insulating behavior is driven by surface interlayer dimerization. These results open intriguing potentialities in surface functionalization and control of electronic structure.

We show that the three commonly employed approaches that define the same dc (or low-frequency) intrinsic linear anomalous Hall response actually lead to different results for intrinsic nonlinear transport. The difference is due to an intrinsic anomalous distribution (IAD). It originates from a nonlinear field effect during scattering, but its value is completely independent of scattering, because it represents the local equilibration of electron wave packets with field corrected energy. The proper definition of intrinsic current that is detectable in experiment must incorporate the effect of IAD. We also show that IAD is indispensable for consistency with fundamental physical relations. In addition, we predict that under ac driving, the intrinsic reponses in rectified and double-frequency channels exhibit distinct frequency dependence, for which we estimate the signals that can be probed in antiferromagnetic CuMnAs.

Altermagnets are a new class of symmetry-compensated magnets with large spin splittings. Here, we show that the notion of altermagnetism extends beyond the realm of Landau-type order: we study exactly solvable ${\mathbb{Z}}_2$ quantum spin(-orbital) liquids (QSLs), which simultaneously support magnetic long-range order as well as fractionalization and ${\mathbb{Z}}_2$ topological order. Our symmetry analysis reveals that in this model three distinct types of “fractionalized altermagnets (${\text{AM}}^{*}$)” emerge, which can be distinguished by their residual symmetries. Importantly, the fractionalized excitations of these states carry an emergent ${\mathbb{Z}}_2$ gauge charge, which implies that they transform projectively under symmetry operations. Consequently, we show that “altermagnetic spin splittings” are now encoded in a momentum-dependent particle-hole asymmetry of the fermionic parton bands. We discuss consequences for experimental observables such as dynamical spin structure factors and (nonlinear) thermal and spin transport.

Quantum Zeno dynamics (QZD), which restricts the system’s evolution to a protected subspace, provides a promising approach for protecting quantum information from noise. Here, we explore a practical approach to harnessing QZD for robust quantum metrology. By introducing strong interparticle interactions during the parameter encoding stage, we overcome the typical limitations of previous QZD studies, which have largely focused on single-particle systems and faced challenges where QZD could interfere with the encoding process. We experimentally validate the proposed scheme on a nuclear magnetic resonance platform, achieving near-optimal precision scaling under amplitude damping in both parallel and sequential settings. Numerical simulations further demonstrate the scalability of the approach and its compatibility with other control techniques for suppressing more general types of noise. These findings highlight QZD as a powerful strategy for noise-resilient quantum metrology.

We report the local-in-time conservative dynamics of nonspinning binary systems at fifth post-Minkowskian (5PM) and first self-force (1SF) orders. This follows from an explicit calculation of the 5PM/1SF nonlocal-in-time tail-type contribution to the deflection angle via worldline effective field theory techniques. Proceeding as in Dlapa et al. [Phys. Rev. Lett. 132, 221401 (2024)], we subtract the nonlocal tail terms from the result in Driesse et al. [Phys. Rev. Lett. 132, 241402 (2024)] and reconstruct a local-in-time Hamiltonian in isotropic gauge—valid for generic orbits. For completeness, we reinstate the nonlocal terms relevant for ellipticlike motion up to 6PN/1SF in a small-eccentricity expansion. Via the connection between the (source) energy flux in Dlapa et al. [Phys. Rev. Lett. 130, 101401 (2023)] and tail effects, we also derive the SF-exact logarithmic-dependent part of the full 5PM bound Hamiltonian. Our results provide the most accurate description to date of the dynamics of bound compact objects within the framework of relativistic scattering computations.

We propose and theoretically analyze methods for quantum many-body control through geometric reshaping of molecular tweezer arrays. Dynamic rearrangement during entanglement is readily available due to the extended coherence times of molecular rotational qubits. We show how motional dephasing can be suppressed and enhanced spin squeezing can be achieved in an actively rearranged short-range XY model. We also analyze in detail a specific static geometry that significantly suppresses decoherence. These general methods as applied to programmable quantum systems offer robust control modalities that are well suited to molecules.

We present a solvable scenario for 3D reconnection in a sheared magnetic field. We consider a localized external force that is applied slowly to a flux tube and then maintained, generating an Alfvénic perturbation that spreads along the field lines. Separation of the sheared field lines reduces the scale of the perturbation across the field, enhancing magnetic diffusion. For a fusion-motivated equilibrium with exponential field-line separation, we find a reconnection timescale proportional to $\mathcal{S}/\ln \mathcal{S}$ under magnetohydrodynamics (MHD) and to ${\mathcal{S}}^{1/3}$ for semicollisional electron-only reconnection, where $\mathcal{S}$ is the Lundquist number of the perturbed flux tube. We generalize these results to arbitrary magnetic geometries, showing that the semicollisional case is geometry independent. Interestingly, we find that slower field-line separation yields an increased reconnection rate in MHD.

We systematically explore the generation of nonlinear charge and spin photocurrents using spin-orbit split surface states. This mechanism enables net DC flow along the surface plane even in centrosymmetric bulk environments like the Rashba prototype Au(111), where we characterize the main quadratic contributions by combining model predictions with density functional calculations. We further identify the Tl/Si(111) surface as a prime scenario for experimental verification; with slight doping, it develops metallic surface states featuring remarkable relativistic properties deviating from the Rashba paradigm, while the bulk remains semiconducting. Its nonlinear charge photocurrent reveals a distinct angular signature and a magnitude comparable to bulk ferroelectrics, highlighting the potential of surface-state photocurrents for low-bias optoelectronic applications. Moreover, the nontrivial spin texture of its surface states enables the generation of pure out-of-plane spin-polarized currents, offering a highly versatile nonlinear spin-filtering functionality beyond the conventional spin Hall effect.

We investigate the physics of fermions on a square lattice with $\pi$ flux, subjected to disordered random ${\mathbb{Z}}_2$ gauge fields that arise from flux defects, i.e., plaquettes with zero flux. At half filling, where the system possesses BDI symmetry, we show that a new class of critical states is realized, with the states at zero energy showing a multifractal character that depends on the flux defect concentration $\mathfrak{c}$ and local correlation between defects. For any concentration of flux defects, we find a nonfreezing multifractal spectrum with a tendency toward termination. We characterize this class of critical states by uncovering a robust relation between the conductivity and the Lyapunov exponent, which is satisfied by the states irrespective of the concentration or the local correlations between the flux defects. We demonstrate that renormalization group methods, based on perturbing the Dirac point, fail to capture this new class of critical states. This Letter not only offers new challenges to the theory of disordered systems in the chiral classes, but is also likely to be useful in understanding a variety of problems where fermions interact with discrete gauge fields.

We present a novel approach that combines machine learning with direct variational energy optimization via the density matrix to solve the Kohn-Sham equation in density functional theory. Instead of relying on the conventional self-consistent field method, our approach directly optimizes the ground state by predicting the density matrix using a neural network, thereby bypassing Hamiltonian matrix diagonalization. Our model employs equivariant neural networks to generate a physically constrained density matrix, enabling stable and efficient energy minimization. This method integrates the construction of training sets directly into the model training process and achieves high accuracy in predicting ground-state properties across various molecular and extended systems, thereby establishing a powerful machine learning paradigm for electronic structure optimization and paving the way for large-scale quantum simulations.

Quantum geometry is crucial for understanding intricate condensed matter systems, governing transport phenomena and optical responses. However, traditional studies of quantum geometry predominantly consider a static crystal lattice, focusing exclusively on the pure-electronic quantum geometry of the Hilbert space parametrized by electronic wave vectors, thereby overlooking the dynamic effects arising from phonons and their coupling with electrons. In this Letter, we reveal the intrinsic quantum geometry of the electron-phonon coupling (EPC), which resides in the hybrid Hilbert space parametrized by both the electronic wave vectors and phonon displacements. The EPC quantum metric, EPC Berry curvature, and EPC shift vector, as central elements, quantify the EPC-induced velocity, polarization, and anomalous charge-center shift, respectively. We further connect this geometry to phonon-mediated optical responses, particularly in-gap resonances, enabling experimental detection and characterization of EPC quantum geometry.

Strain-regulated ferroelectric (FE) materials have long attracted significant attention due to their diverse applications. While soft-phonon theory and the (pseudo) Jahn-Teller effect have achieved considerable success in providing phenomenological descriptions and general understanding, the detailed connection between these perspectives and their microscopic dependence on strain regulation remains unclear. Here, under the framework of density-functional perturbation theory, we demonstrate that the Berry curvature of electron-phonon coupling (EPC) plays a pivotal role in the interatomic force matrix. A subsequent model analysis shows that external strain can reverse the polarity of the EPC Berry curvature in (quasi)degenerate electronic subsystems through band inversion, thereby directly leading to phonon softening. The general theory is then applied to the BiOCl monolayer as a benchmark, which offers an accurate description of the density-functional theory calculations. This mechanism is further observed across a broad range of materials through ab initio calculations, providing an insightful perspective on EPC quantum geometry in lattice dynamics and FE phase transitions.

In most condensed-matter systems, local and collective excitations remain decoupled due to their distinct energy scales. Here, we identify the coupled local-collective excitations in the triangular antiferromagnet ${\mathrm{NaErSe}}_2$, by combining neutron spectroscopy with a total angular momentum modeling. The low-lying crystalline electric field (CEF) doublets include a dipolar ${\mathrm{\Gamma }}_4$ ground state forming a stripe-$x$ order and a ${\mathrm{\Gamma }}_{5,6}$ excited state with dipole-octupole character. High-resolution spectra reveal emergent symmetry-selected dispersions where magnon branches from the ground state are replicated on higher ${\mathrm{\Gamma }}_4$ levels but couple with the ${\mathrm{\Gamma }}_{5,6}$ levels to form a distinct multipolar band. An applied magnetic field reconstructs the CEF wave functions and polarizes the system into a multipolar ferromagnet, further reshaping the spectra. The study demonstrates the emergent coupling of local and collective excitations driven by strong spin-orbit coupling and establishes ${\mathrm{NaErSe}}_2$ as a platform for field-tunable multipolar excitations in frustrated magnets.