A quantum key distribution network enables pairs of users to generate independent secret keys by leveraging the principles of quantum physics. For end-to-end secure communication, a user pair’s secret key must remain secure against any third parties, including both external eavesdroppers and other network users. However, isolating a given user pair from the remaining users while maintaining a high key rate is challenging when all users are intrinsically correlated, particularly in continuous-variable networks. This results in either a low key rate or incomplete end-to-end security. Here, we introduce a multiuser security framework, offering a general and comprehensive end-to-end key rate formula, against the worst-case scenario where an eavesdropper fully exploits the user crosstalk. Building on this framework, we propose a multiuser protocol that achieves the theoretical upper limit in all practical deployments within a 100 km range. Applied to a three-node network, it achieves an Mbps-level per-user key rate and an overall network key rate reaching 90% of the upper limit. The proposed solution supports scalable implementations using telecom-compatible components, while the method for obtaining the accessible information in the network is broadly applicable and can be extended to various multipartite quantum information systems.

The KM3NeT collaboration recently reported the observation of KM3-230213A, a neutrino event with an energy exceeding 100 PeV, more than an order of magnitude higher than the most energetic neutrino in IceCube’s catalog. Given its longer data-taking period and larger effective area relative to KM3NeT, IceCube should have observed events around that energy. This tension has recently been quantified to lie between $2\sigma$ and $3.5\sigma$, depending on the neutrino source. A $\mathcal{O}(100)\mathrm{PeV}$ neutrino detected at KM3NeT has traversed approximately 147 km of rock and sea en route to the detector, whereas neutrinos arriving from the same location in the sky would have only traveled through about 14 km of ice before reaching IceCube. We use this difference in propagation distance to address the tension between KM3NeT and IceCube. Specifically, we consider a scenario in which the source emits sterile neutrinos that partially convert to active neutrinos through oscillations. We scrutinize two such realizations, one where a new physics matter potential induces a resonance in sterile-to-active transitions and another one where off-diagonal neutrino nonstandard interactions are employed. In both cases, sterile-to-active neutrino oscillations become relevant at length scales of $\sim 100\mathrm{km}$, resulting in increased active neutrino flux near the KM3NeT detector, alleviating the tension between KM3NeT and IceCube. Overall, we propose the exciting possibility that neutrino telescopes may have started detecting new physics.

We consider the differential cross-section for single-inclusive jet production with transverse momentum $P_{\perp }$ in deep inelastic scattering at small Bjorken $x_{\text{Bj}}$, mediated by a virtual photon with virtuality $Q^2$. Unlike most studies at small $x$, which focus on particle production in the current fragmentation region, we investigate the kinematic regime where the jet is produced in the target fragmentation hemisphere of the Breit frame, and with $P_{\perp }\ll Q$. For a longitudinally polarized photon, we demonstrate that this cross section is not power suppressed in $P_{\perp }/Q$ and we derive a factorized expression in terms of extended quark and gluon jet fracture functions. Our formula, valid at next-to-leading order in ${\alpha }_s$ at small $x$, is akin to the Altarelli-Martinelli identity for the longitudinal DIS structure function. Numerical estimates show that the extended quark jet fracture function is the most sensitive to saturation effects in large nuclei.

In this Letter, we relate the factorization for $e^{+}{e}^{-}\to h_1{h}_{2}X$ to the factorization for energy-energy correlators in the collinear limit. This enables us to give a nonperturbative proof of factorization for the energy correlators, relate the energy correlator jet function to transverse-momentum-sensitive dihadron fragmentation functions, and provide a rigorous description of the confinement transition region.

We study the QCD scaling behavior of the small-angle energy-energy correlator (EEC), focusing on the transition between its perturbative preconfinement and nonperturbative postconfinement regimes. Applying the light-ray operator product expansion (OPE), we develop a formalism that describes the scaling of the EEC with the input energy $Q$ in the transition and the postconfinement region, where the latter quantum scaling is determined by the $J=5$ DGLAP anomalous dimension. A key result of our Letter is a novel connection between the light-ray OPE and the dihadron fragmentation function (DFF), where we show that the nonperturbative OPE coefficients correspond to moments of the DFF. This finding establishes a new paradigm for studying hadronization. Our theoretical predictions are validated against Monte Carlo simulations for both $e^{+}{e}^{-}$ and $pp$ collisions, showing excellent agreement. The potential role of the quantum scaling in the precision determination of ${\alpha }_s$ is also discussed.

By utilizing the dihadron fragmentation formalism, we extend the previous factorization of near-side energy-energy correlators (EECs) in the collinear limit and derive an all order resummation in the Fourier transform $b_T$-space. A perfect matching is obtained when we compare to the fixed-order results. We further demonstrate the resummation effects for the EECs in $e^{+}{e}^{-}$ annihilation and show that they will significantly improve the theoretical predictions at small angles.

We establish an approach to analyze the free hadron and transition (nonperturbative) regions of near-side energy-energy correlators (EECs) based on dihadron fragmentation functions (DiFFs). We introduce a (nonperturbative) function we call the “EEC DiFF” and explicitly show that expanding it for large relative transverse momentum between the two hadrons gives the $\mathcal{O}({\alpha }_s)$ expression for the “EEC jet” function used in the quark-gluon (perturbative) region. This connection indicates that a formal theoretical matching will be able to bridge the free-hadron region, transition, and quark-gluon regions and allow all of them to be analyzed simultaneously. We further derive a result valid for near-side EECs in the free hadron and transition regions of $e^{+}{e}^{-}$ annihilation in terms of the EEC DiFF. Using a simple model for the function, we perform the first fit within the dihadron framework to experimental data in this regime. We find reasonable agreement with the measurements and reproduce the salient features of near-side EECs in the free hadron and transition regions.

We present a novel emulation scheme for ab initio many-body nuclear calculations that integrates a hierarchical framework with a Bayesian neural network. This approach enables accurate and simultaneous predictions of nuclear properties across entire isotopic chains and is broadly applicable to different regions of the nuclear chart. We benchmark our developments using the oxygen isotopic chain, achieving accurate results for ground-state energies and nuclear charge radii, while providing robust uncertainty quantification. Our framework enables global sensitivity analysis of nuclear binding energies and charge radii with respect to the low-energy constants that describe the nuclear force.

We present direct experimental evidence of laser-induced charge transfer in the dissociative single ionization of an Ar-Kr dimer: $\mathrm{Ar}\text{−}\mathrm{Kr}+n\hslash \omega \stackrel{\text{ionization}}{⟶}\mathrm{Ar}\text{−}{\mathrm{Kr}}^{+}+e^{-}+m\hslash \omega \stackrel{\text{charge transfer}}{⟶}{\mathrm{Ar}}^{+}\text{−}\mathrm{Kr}+e^{-}\stackrel{\text{dissociation}}{⟶}{\mathrm{Ar}}^{+}+\mathrm{Kr}+e^{-}$. Coincidence detection of ${\mathrm{Ar}}^{+}$ fragments and photoelectrons generated by a 400 nm femtosecond pulse shows that ionization initially occurs at the Kr site, followed by charge transfer from Ar to ${\mathrm{Kr}}^{+}$ prior to dissociation. Time-resolved kinetic energy release spectra, obtained with a delayed 800 nm probe, exhibit vibrational revivals that map nuclear wave packet motion on the $X(1/2)$ and $A_2(1/2)$ states of ${\mathrm{Ar}\text{−}\mathrm{Kr}}^{+}$. Relative-phase-controlled two-color fields enable directional control of ${\mathrm{Ar}}^{+}$ emission, with phase-dependent asymmetries reproduced by time-dependent Schrödinger equation simulations, revealing the governing role of wave packet interference in the charge transfer dynamics.

Fluctuations are fundamental in physics and important for understanding and characterizing phase transitions. In this spirit, the phase transition to the Bose-Einstein condensate (BEC) is of specific importance. Whereas fluctuations of the condensate particle number in atomic BECs have been studied in continuous systems, experimental and theoretical studies for lattice systems were so far missing. Here, we explore the condensate particle number fluctuations in an optical lattice BEC across the phase transition in a combined experimental and theoretical study. We present both experimental data using ultracold ${}^{87}\mathrm{Rb}$ atoms and numerical simulations based on a hybrid approach combining the Bogoliubov quasiparticle framework with a master equation analysis for modeling the system. We find strongly anomalous fluctuations, where the variance of the condensate number $\delta N_{\mathrm{BEC}}^2$ scales with the total atom number as $N^{1+\gamma }$ with an exponent around ${\gamma }_{\mathrm{theo}}=0.74(10)$ and ${\gamma }_{\exp }=0.62(9)$, which we attribute to the 2D/3D crossover geometry. Our Letter highlights the importance of the trap geometry on the character of fluctuations and on fundamental quantum mechanical properties.

Ruddlesden-Popper (RP) chalcogenides are an emerging class of layered semiconductors with tunable properties and chemical stability, making them promising candidates for a wide range of functional applications. Over the past four decades, the structural diversity of RP oxides has been exploited to realize advanced functionalities; however, similar strategies have not yet been applied to RP chalcogenides, whose structural behavior remains poorly understood. In this study, we develop a high-accuracy machine-learned interatomic potential to perform large-scale molecular dynamics simulations of the homologous RP series ${\mathrm{Ba}}_{n+1}{\mathrm{Zr}}_n{\mathrm{S}}_{3n+1}$. We identify new polymorphs for each $n$ value, predict the corresponding phase transition temperatures, and validate our approach through comparison with existing experimental data. We find that the $n=1$ phase exhibits in-plane negative thermal expansion, that the $n=1$ and $n=3$ phases undergo unusual ascending symmetry breaking, and that phases with $n\ge 3$ develop layer-dependent tilt patterns not previously observed in inorganic RP compounds. This distinctive behavior arises from the interplay between ${\mathrm{ZrS}}_6$ octahedral rotations and BaS rumpling at the perovskite-rocksalt interface, suggesting new strategies for realizing advanced functionalities and tuning properties in RP chalcogenides.

Anyons, unique to two spatial dimensions, underlie extraordinary phenomena such as the fractional quantum Hall effect, but their generalization to higher dimensions has remained elusive. The topology of Eilenberg-MacLane spaces constrains the loop statistics to be only bosonic or fermionic in any dimension. In this Letter, we introduce the novel anyonic statistics for membrane excitations in four dimensions. Analogous to the ${\mathbb{Z}}_N$ particle exhibiting ${\mathbb{Z}}_{N\times \gcd (2,N)}$ anyonic statistics in two dimensions, we show that the ${\mathbb{Z}}_N$ membrane possesses ${\mathbb{Z}}_{N\times \gcd (3,N)}$ anyonic statistics in four dimensions. Given unitary volume operators that create membrane excitations on the boundary, we propose an explicit 56-step unitary sequence that detects the membrane statistics. We further analyze the boundary theory of $(5+1)\mathrm{D}$ 1-form ${\mathbb{Z}}_N$ symmetry-protected topological phases and demonstrate that their domain walls realize all possible anyonic membrane statistics. We then show that the ${\mathbb{Z}}_3$ subgroup persists in all higher dimensions. In addition to the standard fermionic ${\mathbb{Z}}_2$ membrane statistics arising from Stiefel-Whitney classes, membranes also exhibit ${\mathbb{Z}}_3$ statistics associated with Pontryagin classes. We explicitly verify that the 56-step process detects the nontrivial ${\mathbb{Z}}_3$ statistics in five, six, and seven spatial dimensions. Moreover, in seven and higher dimensions, the statistics of membrane excitations stabilize to ${\mathbb{Z}}_2\times {\mathbb{Z}}_3$, with the ${\mathbb{Z}}_3$ sector consistently captured by this process.

We show that the constrained Ising model on the kagome lattice with infinite first and third neighbor couplings undergoes an infinite series of thermal first-order transitions at which, as in the Kasteleyn transition, linear defects of infinite length condense. However, their density undergoes abrupt jumps because of the peculiar structure of the low temperature phase, which is only partially ordered and hosts a finite density of zero-energy domain walls. The number of linear defects between consecutive zero-energy domain walls is quantized to integer values, leading to a devil’s staircase of topological origin. By contrast to the devil’s staircase of the anisotropic next-nearest neighbor Ising and related models, the wave vector is not fixed to commensurate values inside each phase.

Understanding the optical response of a superconducting microwave resonator is crucial for applications ranging from single-photon detection to quantum transduction between the microwave and optical domains. This topic is gaining significant attention for scaling up quantum computers. However, interactions between the pump light and superconducting resonators often induce unintended resonance frequency shifts and linewidth broadening. In this study, we measure the local optical response of a NbTiN nanowire resonator using a laser-scanning microwave spectroscopy system integrated with a dilution refrigerator. The optical response of the resonator correlates with the resonance modes and position, which we attribute to interactions between two-level systems (TLSs) and laser-induced phonons. These findings establish the TLS-phonon interactions as the dominant mechanism underlying laser-induced resonance variations, providing critical insights for the design and optimization of quantum transducers and superconducting single-photon detectors.

Quantum algorithms for estimating the ground state energy of a quantum system often operate by preparing a classically accessible quantum state and then applying quantum phase estimation. Whether this approach yields quantum advantage hinges on the state’s energy spectrum, that is, the sequence of the state’s overlaps with the energy eigenstates of the system Hamiltonian. We show that the energy spectrum of any entanglement-compressed quantum state must have large support if most energy eigenstates are highly entangled, an assumption supported by the eigenstate thermalization hypothesis. Furthermore, we show that if the compressed quantum state minimizes expected energy, then its energy spectrum decays with the inverse-squared energy eigenvalues under a convex relaxation of the compression constraint. This explains the main empirical finding of Silvester et al. [Phys. Rev. Lett. 134, 126503 (2025).] that the energy spectra of matrix product states do not decay exponentially.

The transfer of information from one part of a quantum system to another is fundamental to the understanding and design of quantum information processing devices. In the realm of discrete systems such as spin chains, inhomogeneous networks have been engineered that allow for the perfect transfer of qubits from one end to the other. Here, by contrast, we investigate the perfect transfer of information in continuous systems, phrased in terms of wave propagation. A remarkable difference is found between systems that possess conformal invariance and those that do not. Systems in the first class enjoy perfect wave transfer (PWT), explicitly shown for one-particle excitations and anticipated in general. In the second class, those that exhibit PWT are characterized as solutions to an inverse spectral problem. As a concrete example, we demonstrate how to formulate and solve this problem for a prototypical class of bosonic theories, showing the importance of conformal invariance for these theories to enjoy PWT. Using bosonization, our continuum results extend to theories with interactions, broadening the scope of perfect information transfer to more general quantum systems.

Optical spin textures with nontrivial topology hold promise for structured light and photonic information processing, yet their generation typically relies heavily on externally structured light with care. This raises questions about their universal existence and true robustness. Here, we uncover and experimentally verify a meronlike spin texture that emerges intrinsically in focused fields, without any wavefront engineering. This intrinsic meron spin texture, unlike their externally engineered counterparts, exhibits exceptional robustness against a wide range of inputs, including partially polarized and spatially disordered pupils corrupted by decoherence and depolarization. We attribute its resilience to the intrinsic property of the focusing process and the topological protection from phase vortices in the focal field. Our findings reveal a naturally occurring spin structure that is intrinsic to the focused field with exceptional robustness against noise, which complements the existing externally engineered ones. It offers new ingredients into topological spin textures in optics and enriches their potentials for disorder-resilient photonic applications.

Multiturn charge-exchange injection is the primary method of creating high-intensity hadron beams in circular accelerators, and phase space painting during injection enables tailoring of the accumulated phase space distribution. A technique we call eigenpainting allows injection of particles into a single mode of a coupled ring, providing full four-dimensional control of the phase space distribution. Under ideal conditions, uniform eigenpainting generates a linear-force equilibrium distribution in the transverse plane, with zero volume in four-dimensional transverse phase space, even including space charge. We have implemented eigenpainting for the first time in the spallation neutron source accumulator ring. Injecting $8.8\mathrm{\mu }\mathrm{C}$ of an 800 MeV beam, we obtain a final ratio of intrinsic transverse emittances of $\approx 2.4$. We analyze the effect of space charge on the final distribution through comparison of the reconstructed phase space to particle-in-cell simulations.

We examine the Ramo current in a nanoscale planar vacuum diode undergoing field emission in the presence of a DC voltage supply and an external resistor. We describe a simple mechanism for generating persistent current oscillations in the diode due to the voltage drop across the external resistor (beam loading), which reduces the total field and inhibits the emission. The amplitude and the frequency, which is in the THz domain, depend on the operating parameters of the diode. Molecular dynamics simulations are used to find the characteristics and physical basis of the mechanism, and a simple analytical model is presented, in good agreement with the simulation.