We study the frustration pattern of a square lattice with in situ fabricated Nb-Pt-Nb four-terminal Josephson junctions. The four-terminal geometry gives rise to a checkerboard pattern of alternating fluxes $f$, $f^{\prime }$ piercing the plaquettes, which stabilizes the Berezinskii-Kosterlitz-Thouless transition even at irrational flux quanta per plaquette, due to an unequal repartition of integer flux sum $f+f^{\prime }$ into alternating plaquettes. This type of frustrated frustration manifests as a beating pattern of the dc resistance, with state configurations at the resistance dips gradually changing between the conventional zero- and half-flux states. Hence, the four-terminal Josephson junction array offers a promising platform to study previously unexplored flux and vortex configurations and provides an estimate on the spatial expansion of the four-terminal Josephson junction central weak link area.

Multipoint correlations in randomly heterogeneous composite media are determined by the probability that a set of points belong to specific phases. They determine a wide range of macroscopic transport properties such as conductivity, dielectric constant, diffusion coefficient, and transmittance. The Poisson model—a random tesselation of space by hyperplanes—provides realistic descriptions of heterogeneous media in, e.g., radiation-transport applications; yet, until now, it has lacked closed-form expressions for its multipoint correlations. We resolve this problem by presenting an exact solution for the multipoint correlations in the Poisson model. By comparing it to Monte Carlo simulations of four-point correlations in three dimensions, we demonstrate the accuracy of our solution. We visualize the multipoint correlations and discuss their features.

We investigate spin-rectification phenomena in canted antiferromagnets, closely connected to the family of altermagnetic materials. Our results show that excitation efficiency is significantly enhanced by the Dzyaloshinskii-Moriya interaction. Antiferromagnetic dynamics can be detected through spin-Hall magnetoresistance and bolometric effects, with an efficiency reaching up to $\mathrm{mV}/\mathrm{W}$. The rectified voltage is influenced by the symmetry of the exciting torques, detection mechanisms (continuous spin-pumping and spin-Hall magnetoresistance), and the antiferromagnetic crystalline axis. Under high pumping power, we observe a saturation effect related to Suhl-like spin-wave instabilities and a nonlinear redshift of the antiferromagnetic resonance. These findings open new avenues for studying nonlinear dynamics in antiferromagnetic and altermagnetic spintronic devices.

Discovery of new states of matter is a key objective in modern condensed matter physics, which often leads to revolutionary technological advancements such as superconductivity. Quantum spin nematic, a “hidden order” that evades conventional magnetic probes, is one such state. ${\mathrm{Na}}_2\mathrm{BaNi}({\mathrm{PO}}_4{)}_2$ is a potential spin nematic material, suggested by the observation of a two-magnon Bose-Einstein condensation from above the saturation field. However, direct confirmation of the spin nematicity remains elusive. This Letter presents inelastic neutron scattering spectra from the putative spin nematic phases of ${\mathrm{Na}}_2\mathrm{BaNi}({\mathrm{PO}}_4{)}_2$, revealing low-energy quadrupole waves that are absent in the neighboring conventional magnetic phases. A spin-one model quantitatively captures the full details of the spin excitation spectra across all low-temperature phases, providing direct evidence of the spin nematic orders. Additionally, we show evidence of the three-magnon continuum and two-magnon bound states in the $1/3$-magnetization plateau, revealing condensation of the two-magnon bound state as the origin of the low-field spin nematic supersolid phase.

Dispersion is ubiquitous in nature as a result of causality, and dispersive time-varying materials have been widely used in the experimental realization of photonic time-varying media. Here, we derive the Floquet Hamiltonian and formulate Maxwell’s equations of dispersive time-varying media as a Floquet matrix eigenproblem. The derived Floquet Hamiltonian allows us to investigate the band structures and eigenmodes of the system. Using the eigenmodes, we identify the Floquet $\pi$ exceptional points by tracking the variation of Aharonov-Anandan phase. Our theory rigorously reformulates existing models and facilitates the development of Floquet Green’s function and resonant mode expansion in open photonic time-varying systems.

Quantum entanglement serves as an essential resource for quantum information technology. In many realistic quantum information tasks, it is necessary to reliably verify entanglement even when the measurement devices are unreliable. In this Letter, we experimentally demonstrate measurement-device-independent verification of continuous-variable (CV) entanglement. We show that the conventional CV entanglement witness may falsely identify a separable state as a CV entangled state when the measurement devices are unreliable. To eliminate such need for trusted measurement devices, we implement a measurement-device-independent entanglement witness for verifying CV entanglement and demonstrate its resilience against local oscillator power and phase modifications. Our Letter sheds light on advancing high-security quantum information processing and its practical implementation in quantum networks.

Quantifying the resources available to a quantum computer appears to be necessary to separate quantum from classical computation. Among them, entanglement, nonstabilizerness, and coherence are arguably of great significance. We introduce “path coherence” as a measure of the coherent path interferences arising in a quantum computation. Leveraging the sum-over-paths formalism, we obtain a classical algorithm for estimating quantum transition amplitudes, the complexity of which scales with path coherence. As path coherence relates to the hardness of classical estimation of quantum transition amplitudes, it provides a new perspective on the role of coherence in quantum computational advantage. Beyond their fundamental significance, our results have practical applications for simulating large classes of quantum computations with classical computers.

The coherent storage, buffering and retrieval of photons in a quantum memory enables the scalable creation of photonic entangled states via linear optics and repeat-until success, unlocking applications in quantum communications and photonic quantum computing. Quantum memories based on off-resonant cascaded absorption (ORCA) in atomic vapors allow this storage to be broadband, noise free, and high efficiency. Here, we implement a cavity-enhanced ORCA memory with reduced footprint and reduced power requirements compared to conventional single-pass schemes. By combining a strong magnetic field with polarization control, we maintain a Doppler-free interaction and eliminate the need for optical pumping. Our design establishes the feasibility of large arrays of ultracompact, low-power, near-unit efficiency, noiseless quantum memories running at GHz bandwidth, without the need for atom trapping or cryogenics.

It is shown that both standard general relativity (GR) and Chern-Simons (CS) gravity, the latter containing chiral gravitational anomaly terms, seed the production of pairs of entangled gravitons in a multi-mode squeezed state. This involves the interaction of gravitons with the axionic cloud surrounding a superradiant Kerr (rotating) black hole background. The order of magnitude of the squeezing effect, specifically the number of graviton excitations in the squeezed vacuum, is estimated in the nonrelativistic limit, relevant for the superradiance process. It is found analytically that the squeezing from the GR process of annihilation of two axions into two gravitons, dominates, by many orders of magnitude, that coming from the axion decay into two gravitons, induced by the higher-derivative CS term. It is also shown that significant squeezing effects are produced in the case of long-lived axionic clouds, whose lifetimes are much longer than the timescale for which superradiance is effective. A brief discussion on current exclusion (for the first time) of very long axion-cloud lifetimes, through comparison of our results with current LIGO data, as well as potential detection of such effects in future interferometers is also given.

On shell methods have found a new application to local observables such as asymptotic radiation fields and gravitational waveforms. While these observables are invariant under small gauge transformations, they are known to depend on a choice of asymptotic gauge; in gravity on asymptotically Minkowski spacetimes, this is a choice of Bondi-Van der Burg-Metzner-Sachs frame. In this Letter, we provide a method for capturing these supertranslations, to all orders in perturbation theory, using the on shell framework of scattering amplitudes.

One of the important open problems in quantum black hole physics is a dual interpretation of holographic complexity proposals. To date the only quantitative match is the equality between the Krylov spread complexity in the triple-scaled Sachdev-Ye-Kitaev (SYK) model and the complexity $=$ volume proposal in classical Jackiw-Teitelboim gravity. Our Letter utilizes the recent connection between the double-scaled SYK model and sine dilaton gravity to show that the quantitative relation between Krylov spread complexity and complexity $=$ volume extends to finite temperatures and to full quantum regime on the gravity side at disk level. Furthermore, we isolate the first quantum correction to the complexity $=$ volume proposal and propose to view it as a complexity of quantum fields in the bulk. The key lesson from our Letter is that gravity demands to assign complexity also to Euclidean state preparation.

The T2K Collaboration presents the first measurement of electron neutrino-induced charged-current pion production on a predominantly carbon target in a restricted kinematical phase space. This is performed using data from the 2.5° off-axis near detector, ND280. The differential cross sections with respect to the outgoing electron and pion kinematics, in addition to the total flux-integrated cross section, are obtained. Comparisons between the measured and predicted cross-section results using the neut, genie, and nuwro Monte Carlo event generators are presented. The measured total flux-integrated cross section is $[2.52\pm 0.52(\mathrm{stat})\pm 0.30(\mathrm{syst})]\times {10}^{-39}{\mathrm{cm}}^2{\text{nucleon}}^{-1}$, which is lower than the event generator predictions.

Using data samples with a total integrated luminosity of $253{\mathrm{pb}}^{-1}$ collected by the BESIII detector operating at the BEPCII collider, the differential cross sections of inclusive ${\pi }^{\pm }$ and $K^{\pm }$ production, as a function of the momentum and normalized by the total hadronic cross section, are measured at center-of-mass energies from 2.000 to 3.671 GeV. The measured ${\pi }^{\pm }$ cross sections are consistent with the previously reported ${\pi }^0$ cross sections by BESIII, while the $K^{\pm }$ cross sections are systematically higher than the $K_S^0$ cross sections by a factor of approximately 1.4. These new results are in agreement with state-of-the-art QCD analyses at next-to-next-to-leading-order accuracy, particularly in the large hadron momentum region at energy scales down to 3 GeV. These findings support the validity of isospin symmetry in parton fragmentation processes.

Nucleon structure functions, as measured in lepton-nucleon scattering, have historically provided a critical observable in the study of partonic dynamics within the nucleon. However, at very large parton momenta, it is both experimentally and theoretically challenging to extract parton distributions due to the probable onset of nonperturbative contributions and the unavailability of high-precision data at critical kinematics. Extraction of the neutron structure and the d quark distribution have been further challenging because of the necessity of applying nuclear corrections when utilizing scattering data from a deuteron target to extract the free neutron structure. However, a program of experiments has been carried out recently at the energy-upgraded Jefferson Lab electron accelerator aimed at significantly reducing the nuclear correction uncertainties on the d quark distribution function at large partonic momentum. This allows leveraging the vast body of deuterium data covering a large kinematic range to be utilized for d quark parton distribution function extraction. In this Letter, we present new data from experiment E12-10-002, carried out in Jefferson Lab Experimental Hall C, on the deuteron to proton cross section ratio at large Bjorken $x$. These results significantly improve the precision of existing data and provide a first look at the expected impact on quark distributions extracted from parton distribution function fits.

This manuscript reports on the direct observation of a $\beta$-delayed two-neutron emission in a study of ${}^{134}\mathrm{In}$ at the ISOLDE Decay Station using neutron spectroscopy. We also report on the first measurement in ${\beta }^{-}$ decay of the long-sought $13/2^{+}$ excited state in ${}^{133}\mathrm{Sn}$, attributed to be the neutron single-particle $i_{13/2}$ orbital. The observation of sequential neutron emission is used to extract the relative population of the $i_{13/2}$ state, which was found to be much smaller than the predictions of the statistical model. The experiment was possible because of the innovative use of a neutron array with neutron discrimination and interaction tracking capabilities. This is the first study of the details of the two-neutron emission for a nucleus, which belongs to the $r$-process path. Understanding $\beta$-delayed two-neutron emission probabilities is essential to validate models used in astrophysical $r$-process nucleosynthesis calculations. Observing two-neutron emissions in ${\beta }^{-}$ decay paves the way for new experiments to study energy and angular correlations for $\beta$-delayed multineutron emitters.

We present an ab initio study of the charge and matter radii of oxygen isotopes from ${}^{16}\mathrm{O}$ to ${}^{20}\mathrm{O}$ using nuclear lattice effective field theory (NLEFT) with high-fidelity ${\mathrm{N}}^3\mathrm{LO}$ chiral interactions. To efficiently address the Monte Carlo sign problem encountered in nuclear radius calculations, we introduce the partial pinhole algorithm, significantly reducing statistical uncertainties and extending the reach to more neutron-rich and proton-rich isotopes. Our computed charge radii for ${}^{16}\mathrm{O}$, ${}^{17}\mathrm{O}$, and ${}^{18}\mathrm{O}$ closely match experimental data, and we predict a charge radius of 2.810(32) fm for ${}^{20}\mathrm{O}$. The calculated matter radii show excellent agreement with values extracted from low-energy proton and electron elastic scattering data, but are inconsistent with those derived from interaction cross sections and charge-changing cross section measurements. These discrepancies highlight model-dependent ambiguities in the experimental extraction methods of matter radii and underscore the value of precise theoretical benchmarks from NLEFT calculations.

The rapid proton-capture process is one of the primary, explosive thermonuclear burning processes that drive type I x-ray bursts. A possible termination of the rapid proton-capture process at around ${}^{84}\mathrm{Mo}$ was previously suggested by the formation of a ZrNb cycle. We report here precision mass measurements at around ${}^{84}\mathrm{Mo}$ that conclude the issue regarding the possibility of the cycle. The experiment was conducted using the multireflection time-of-flight spectrograph at RIKEN Radioactive Isotope Beam Factory, and the masses of ${}^{79}\mathrm{Y}$, ${}^{83}\mathrm{Nb}$, ${}^{84}\mathrm{Mo}$, ${}^{88}\mathrm{Ru}$, and an isomer in ${}^{78}\mathrm{Y}$ were measured. For ${}^{84}\mathrm{Mo}$, ${}^{88}\mathrm{Ru}$, and the isomeric state of ${}^{78}\mathrm{Y}$, their masses were experimentally determined for the first time with uncertainties of $\delta m\approx 20\mathrm{keV}/{\mathrm{c}}^2$. The mass precisions of ${}^{79}\mathrm{Y}$ and ${}^{83}\mathrm{Nb}$ were improved to 13 and $9.6\mathrm{keV}/{\mathrm{c}}^2$, respectively. The new $\alpha$-separation energy of ${}^{84}\mathrm{Mo}$, 1.434(83) MeV, unambiguously rules out the possibility of forming the ZrNb cycle. The x-ray burst simulation with the new masses shows that our measurements effectively remove the large final abundance uncertainties in the $A=80–90$ mass region. The new mass values improve the prediction power for the composition of the nuclear ashes in x-ray bursts.