Optical frequency combs, named for their comblike peaks in the spectrum, are essential for various sensing applications. As the technology develops, its performance has reached the standard quantum limit dictated by the quantum fluctuations of coherent light field. Quantum combs, with their quantum fluctuation engineered via squeezing and entanglement, are the necessary ingredient for overcoming such limits. We develop the theory for designing and analyzing quantum combs, focusing on dual-comb interferometric measurement. Our analyses cover both squeezed and entangled quantum combs with division receivers and heterodyne receivers, leading to four protocols with quantum advantages scalable with squeezing/entanglement strength. In the spectroscopy of a single absorption line, the division receiver with the squeezed comb suffers from entanglement-mismatching-induced amplified noise, while the other three protocols demonstrate a surprising robustness to loss at a few comb lines. Such a unique loss-robustness of a scalable quantum advantage has not been found in any traditional quantum sensing protocols.

The realization of compact laser-plasma accelerator (LPA) driven free electron lasers (FELs) has been attempted for nearly two decades, yet, difficult to overcome electron beam quality and stability issues prevented FEL lasing until recently. LPA based FEL is now demonstrated in both the self-amplified spontaneous emission and the fully coherent seeded modes, albeit for the latter only in the low-gain regime. Here, we report on the observation of the high-gain regime in the seeded configuration, opening the path to FEL saturation. Exponential FEL signal growth was established through an increase in spectral charge density of the electron beam. Within a 2 m long undulator and with a gain length of 0.55 m, FEL pulse energies of 45 nJ were achieved at wavelengths of around 272 nm, in good agreement with quantitative numerical simulations. The effects of a systematic variation of the seed pulse duration and thus power via pulse chirping was studied in detail, a refinement up to now reserved to radio-frequency accelerator based FELs. These results encourage the future scaling to shorter wavelengths.

Asymmetry of the compressed fusion fuel configuration, as characterized by a variation in areal density, in inertial confinement fusion (ICF) implosions is a known performance limitation. While ignition has been achieved on the National Ignition Facility (NIF), implosion symmetry was not perfect, and subsequent experiments that have extended fusion performance still struggle with symmetry control and would, in principle, perform much better if the areal density uniformity of the fuel was improved by eliminating thin regions in the DT (Deuterium-Tritium) fuel that develop by the time of peak compression. In indirect drive (IDD), altering the time-dependent laser cone fraction and cross-beam energy transfer are the usual tactics for controlling implosion asymmetry in IDD target designs, but it may be that those tools have been pushed to their limits. In this Letter, we present a new tactic for controlling the implosion using satellite ablating pellets to manipulate the time-dependent x-ray field around an ICF capsule. In theory and in simulations the action of these pellets is quite effective at reducing the swing of x-ray drive from waist hot to pole hot, thus achieving a more one-dimensional fuel configuration at peak compression. Simulations show that a factor of $\sim 2$ in yield performance can be obtained via this technique, when applied to past record implosions on the NIF. Some speculative alternate uses of the proposed target concept are also mentioned in the conclusion of this Letter.

High-pressure superconductivity in metal monochalcogenides has been ascribed to disorder-driven Anderson localization [Phys. Rev. Lett. 134, 196001 (2025)]. Using density-functional perturbation theory and Migdal-Eliashberg calculations, we show that superconductivity in BiSe, PbSe, PbS, and HgS is instead governed by a universal intrinsic mechanism. Under pressure, the superconducting transition temperature is fully regulated by conventional electron-phonon coupling and decreases monotonically with pressure due to phonon hardening and a reduced density of states at the Fermi level. The increase of $T_c$ previously reported upon decompression arises from the recovery of stronger intrinsic coupling in metastable low-pressure phases, without invoking disorder or localization effects previously used to explain this phenomenon. Our results establish a unified phonon-mediated description of superconductivity in metal monochalcogenides and solve conflicting interpretations.

A two-dimensional topologically nontrivial state of noninteracting electrons, such as the surface state of a three-dimensional topological insulator, is predicted to realize a topological superconductor when proximity-coupled to an ordinary $s$-wave superconductor. In contrast, noninteracting electrons partially occupying a Landau level, with Rashba spin-orbit coupling that lifts the spin degeneracy, fail to develop topological superconductivity under similar proximity coupling in the presence of the conventional Abrikosov vortex lattice. We demonstrate, through exact diagonalization, that introducing in this model a repulsive interaction between electrons induces topological superconductivity at half-filled Landau level for a range of parameters. This appears rather surprising because a repulsive interaction is expected to inhibit, not promote, pairing, but suggests an appealing principle for realizing topological superconductivity: proximity-coupling a composite Fermi liquid to an ordinary $s$-wave superconductor.

In Markov networks, measurement blackouts with unknown frequency compromise observations such that thermodynamic quantities can no longer be inferred reliably. In particular, the observed currents neither discern equilibrium from nonequilibrium nor can they be used in extant estimators of entropy production. Our strategy to eliminate these effects is based on formally attributing the blackouts to a second channel connecting states. The unknown frequency of blackouts and the true underlying transition rates can be determined from the short-time limit of observed waiting-time distributions. A postmodification of observed trajectory data yields a virtual effective dynamics from which the lower bound on entropy production based on thermodynamic uncertainty relations can be recovered fully. Moreover, the postprocessed data can be used in waiting-time based estimators. Crucially, our strategy does not require the blackouts to occur homogeneously or symmetrically under time reversal.

The tube model has long served as a cornerstone of entangled polymer dynamics and rheology. We test some of the key concepts of the tube model by investigating the equilibrium dynamics of a free chain in a fixed-topology polymer network using molecular dynamics simulation. Our results reveal significant position-dependent dynamical heterogeneity manifested as a rugged free energy landscape for the longitudinal motion, resulting in additional friction due to the topological interactions, and a “tube dilation” mechanism arising from the relaxation of entanglements formed by loop strands in the network in a “flip-flop” motion. On timescales less than the Rouse time, the mean-square displacement of the center of mass of the free chain displays a subdiffusive behavior that is slower than the expected $t^{1/2}$ scaling. On longer timescales, the effects of topological friction amount to a renormalized monomer friction that is several times the intrinsic value. These results challenge some of the fundamental assumptions of the tube model, even under equilibrium conditions.

We present particle-resolved simulations of dense frictional suspensions undergoing the viscous-inertial transition using pressure-imposed rheology. By varying the fluid viscosity, shear rate, and granular pressure, we demonstrate that the transition occurs at a Stokes number of $\approx 8$ (close to the value of 10 found in the experiments of Tapia et al. [Viscous to inertial transition in dense granular suspension, Phys. Rev. Lett. 129, 078001 (2022).]) and also that the shear stress exhibits a slower transition than the particle pressure. Using our highly resolved numerical simulations, we further demonstrate that this transitional behavior is related to the combined effect of tangential contact and lubrication forces, as the frictional particles concurrently shift from rolling to sliding contacts. This shift is controlled not only by the Stokes number, but also by the distance from jamming. Additionally, we examine the role of increasing interparticle friction on the viscous-inertial transition.

The evolution of a system coupled to baths is commonly described by a master equation that, in the long-time limit, yields a steady-state density matrix. However, when the same evolution is unraveled into quantum trajectories, it is possible to observe a transition in the scaling of entanglement within the system as the system-bath coupling increases—a phenomenon that is invisible in the trajectory-averaged reduced density matrix of the system. Here, we go beyond the paradigm of trajectories from master equations and explore whether a qualitatively analogous entanglement-scaling transition emerges in a single unitary evolution of the combined system-bath setup, without monitoring the dynamics of the system. We investigate the scaling of entanglement in a unitary quantum setup composed of a two-dimensional lattice of free fermions, where each site is coupled to a fermionic bath. As the system-bath coupling increases, the logarithmic fermionic negativity reveals an entanglement transition from logarithmic-law to area-law scaling. This occurs while the system’s steady-state properties are trivial, highlighting that the signatures of these different scalings are within the bath-bath correlations. Evidence of the transition is also found in the mutual information and the correlations of the full system-bath setup, suggesting that the entanglement transition is underpinned by a change in the spatial structure of quantum information.

Quantum many-body scars (QMBS) have attracted considerable interest due to their role in weak ergodicity breaking in many-body systems. We present a general construction that embeds stabilizer states as QMBS of local Hamiltonians. The method relies on a notion of factorizability of Pauli strings on a lattice, which is used to convert stabilizer elements into local, few-body operators that annihilate the stabilizer state. This enables the systematic construction of parent Hamiltonians with zero-energy stabilizer QMBS typically near the middle of the spectrum. The method reproduces several known results in a unified framework, including recent examples of volume-law entangled QMBS, such as the “rainbow” QMBS and the entangled antipodal Bell pair state. We also apply the framework to construct examples of stabilizer QMBS with a more complex entanglement structure, such as the cluster state, the toric code state, and a volume-law entangled state we dub the antipodal toric code state. Exact diagonalization confirms our results and reveal the stabilizer states as exact eigenstates of their parent Hamiltonian.

In this Letter, we initiate a systematic study of the $n$-point correlation functions (CFs) in gauge theories in the sequential light-cone (SLC) limit. Focusing on QCD, we formulate a factorization theorem for the CF of four vector currents in this limit using tools from soft-collinear effective field theory (SCET). This result unveils a duality between CF and Wilson loops in nonconformal field theories, according to which the singular structure of the CF is described by a null polygonal Wilson loop dressed by universal jet functions and current form factors, directly related to well-known ingredients in collider physics. We employ this new factorization theorem to obtain the singular terms of the four-point CF in QCD in the SLC limit up to three loops. This constitutes the first determination of terms beyond one loop, and in particular, determines, for the first time, conformal-symmetry-breaking terms induced by the nonvanishing $\beta$ function of QCD. As a stringent check, we verify that our result satisfies the anomalous conformal Ward identities and that its leading transcendental term reproduces the known correlation function in $\mathcal{N}=4$ SYM to three loops. Our results are easily generalized to the multipoint case, offering a powerful tool for future applications of SCET to the study of the fundamental structure of gauge theories.

We report on three improvements in the context of Feynman integral reduction and $ϵ$-factorized differential equations. First, we show that with a specific choice of prefactors, we trivialize the $ϵ$ dependence of the integration-by-parts identities. Second, we observe that with a specific choice of order relation in the Laporta algorithm, we directly obtain a basis of master integrals, whose differential equation on the maximal cut is in Laurent polynomial form with respect to $ϵ$ and compatible with a particular filtration. Third, we prove that such a differential equation can always be transformed to an $ϵ$-factorized form. This provides a systematic algorithm to obtain an $ϵ$-factorized differential equation for any Feynman integral. Furthermore, the choices for the prefactors and the order relation significantly improve the efficiency of the reduction algorithm.

The trace anomaly of dense matter, $\mathrm{\Delta }\equiv 1/3-P/ϵ$, defined through the ratio $w\equiv P/ϵ$ of pressure $P$ to energy density $ϵ$, quantifies deviations from conformal symmetry and provides a dimensionless measure of the stiffness of the equation of state (EOS) relevant for both neutron stars and heavy-ion collisions. While $\mathrm{\Delta }(ϵ)$ has recently been inferred from neutron star observations, we report the first Bayesian extraction of the trace anomaly from collective flow observables in intermediate-energy heavy-ion collisions. By employing transport-model simulations that explicitly decouple the cold matter mean-field potential from thermal effects, we directly constrain the EOS of cold dense matter. Remarkably, the trace anomaly inferred from laboratory flow data agrees quantitatively, within 68% credible intervals, with independent astrophysical posterior bands. This nontrivial agreement demonstrates that heavy-ion collisions and neutron star observations probe the same macroscopic properties in a mutually consistent way, establishing the dense-matter trace anomaly as a composition-insensitive macroscopic bridge observable across widely different physical environments.

Chiral phonons carry finite phonon angular momentum, yet their momentum-resolved behavior in acoustic branches remains largely unexplored. Here, we report the direct detection of chiral acoustic phonons in elemental Te. Through a combination of high-energy-resolution inelastic x-ray scattering experiments and atomistic modeling, we confirm that longitudinal acoustic modes develop pronounced circular atomic motion by mixing with transverse modes. Our results establish a direct link between unexpected scattering intensity in nominally forbidden geometries and circular phonons, offering a framework for characterizing momentum-resolved phonon chirality and highlighting the emergence of intrinsic phonon angular momentum in acoustic branches.

Qutrits offer the potential for enhanced quantum computation by exploiting an enlarged Hilbert space. However, the synthesis of high-fidelity and fast qutrit gates, particularly for single qutrits, remains an ongoing challenge, as it involves overcoming intrinsic constraints in quantum platforms. Here, we develop a novel framework for the efficient implementation of a single-qutrit gate set via coherent control, leveraging SU(3) dynamics while obviating platform-specific constraints such as those arising from the selection rule. As a proof-of-principle demonstration, we realize 35-ns qutrit hadamard and x gates using a superconducting transmon, achieving an average fidelity of 99.5%, as verified by randomized benchmarking. We further demonstrate two paradigmatic quantum circuits, which can be naturally extended to scalable qudit algorithms for phase estimation and parity check. In addition, we propose an SU(3)-based decomposition strategy for an arbitrary single-qutrit gate and numerically demonstrate its substantial efficiency improvement over conventional SU(2)-based protocols. By addressing the challenge of efficiently implementing single-qutrit gates, our protocol paves the way for realizing high-performance qutrit processors in diverse quantum platforms.

The Galactic Center Excess (GCE) may yet herald the discovery of annihilating dark matter. Weighing against that conclusion are analyses showing evidence for dim point sources within the spatial structure of the emission. Because of technical limitations these analyses are purely spatial with all spectral information that could disentangle the excess from astrophysical backgrounds discarded. Here, we demonstrate that a neural network simulation-based inference approach can jointly analyze the spatial and spectra data. The addition is profound: energy information drives the putative point sources to be significantly dimmer, indicating either the GCE is truly diffuse in nature or made of an exceptionally large number of sources. Quantitatively, for our best fit background model, the excess is essentially consistent with Poisson emission as predicted by dark matter. If due to point sources, our median prediction is $\mathcal{O}({10}^5)$ sources, or more than 35 000 at 90% confidence—both orders of magnitude larger than the hundreds preferred by earlier point-source analyses of the GCE, although variations allowed by background systematics could reduce the required number of sources by roughly an order of magnitude.

The James Webb Space Telescope has uncovered a population of compact, high-redshift sources, the Little Red Dots (LRDs), which may host supermassive black holes (BHs) significantly heavier than their stellar content compared with local scaling relations. These objects challenge standard models of early galaxy formation and may represent an extreme class of early BH hosts. In this Letter, we investigate whether these BHs could have a primordial origin. We first show that the direct formation of these BH masses in the early Universe is excluded by stringent cosmic microwave background $\mu$-distortion limits. We then investigate the assembly of massive BHs from lighter, observationally allowed primordial black holes (PBHs) via hierarchical mergers, finding that, although this channel can operate depending on the merger history, it faces challenges in explaining the observations due to the rarity of the required high-redshift dark matter halos. Finally, we estimate gas accretion onto intermediate-mass PBHs, while jointly tracking metallicity evolution, and identify regions of parameter space in which such growth could reproduce the observed properties of LRDs. As a special case, we focus on the strongly lensed source QSO1, whose extremely low metallicity and large mass provide a stringent test of these formation channels.

We present a search for an invisible hidden-sector particle $X_{\mathrm{inv}}$, produced in $B^0\to {\overline{D}}^0{X}_{\mathrm{inv}}$ and $B^{\pm }\to h{X}_{\mathrm{inv}}$ decays, where $h={\pi }^{\pm }$, $K^{\pm }$, $D_s^{\pm }$, $p^{\pm }$. The search is performed using $e^{+}{e}^{-}$ collision data recorded with the Belle detector, corresponding to $711{\mathrm{fb}}^{-1}$. No significant signal is observed. We set 90% confidence level upper limits ranging between ${10}^{-4}$ and ${10}^{-6}$ on the branching fraction $\mathcal{B}(B\to h{X}_{\mathrm{inv}})$ as a function of $m_{X_{\mathrm{inv}}}$. Corresponding limits are set on $\mathcal{B}(B\to hX)\times \mathcal{B}(X\to \gamma \gamma )$ for lifetimes $c{\tau }_X$ between $10\mathrm{\mu }\mathrm{m}$ and 10 m. Many of these limits are the first direct constraints on their respective decays. Our results provide the most stringent exclusion limits to date on the branching fractions for all search channels, and exclude previously unexplored regions of parameter space relevant to several new physics models.