Externally seeded free-electron lasers (FELs) provide radiation with full longitudinal and transverse coherence in the extreme ultraviolet and soft x-ray spectral ranges, inaccessible to conventional laser sources. Until now, externally seeded operation has been limited to the extreme ultraviolet and soft x-ray regime, while shorter wavelengths have been accessed primarily through stochastic self-amplified spontaneous emission processes (or derivatives thereof, one based on self-seeding) or through nonlinear harmonic generation at strongly reduced pulse energy. At the FERMI FEL facility, we have demonstrated stable operation in high-gain harmonic generation (HGHG) covering the nitrogen K-edge, most of the water-window spectral range, and approaching the oxygen K-edge by combining short-wavelength ultraviolet seeding (200 nm), increased electron beam energy, and preservation of an ultralow relative slice energy spread at the ${10}^{-5}$ level. The emitted radiation at such short wavelengths still exhibits the typical narrow bandwidth and wavelength stability of the HGHG scheme enabling, for example, time-resolved x-ray absorption spectroscopy measurements. Longitudinally coherent emission at 1 nm is obtained as the third harmonic of the fundamental FEL emission. Despite the lower intensity typical of nonlinear harmonic emission, these results demonstrate that external seeded FELs can be extended to nanometer wavelengths, establishing deterministic, fully coherent soft x-ray generation and surpassing the previous wavelength operation limits. This advance opens new opportunities for coherent control and nonlinear x-ray experiments that require both high photon energy and longitudinal coherence, and demonstrates a promising pathway toward further extension of externally seeded FELs to shorter wavelengths.

Quorum sensing (QS) is known in biology as a form of intercellular communication mediated by signaling molecules called autoinducers. The QS protocol governs the transition from individual to collective cell behavior once a critical population density is reached. Using numerical simulations, we investigate how defects influence the QS transition and the structural organization of the resulting colonies. Our model system consists of a mixture of slow (“cold”) and fast (“hot”) diffusing colloidal particles that obey the QS protocol, together with defect particles characterized by a constant diffusivity. A striking reentrant solidification of QS particles, characterized by long-range order, is induced by hot defects, whereas cold defects give rise to amorphous structures with only short-range order. These findings deepen our understanding of the QS interaction and provide a mechanism to control the degree of organization in QS systems, with potential applications in robotics, social sciences, and medicine—for instance, in overcoming antimicrobial resistance.

We present a single-orbital tight-binding model for the low-energy electronic states of the chiral one-dimensional hybrid organic-inorganic lead halide perovskite $(R/S\text{−}\mathrm{PEA}){\mathrm{PbI}}_3$. The model is constructed from a single effective orbital on each of the four symmetry-related sites in the primitive unit cell and incorporates layer, in-plane sublattice, and spin degrees of freedom. With separate parameter sets for the conduction and valence bands, the effective Hamiltonian reproduces the overall band dispersions obtained from density-functional-theory calculations and quantitatively captures the spin splittings near the band edges. It also captures the leading spin-polarization patterns of the Bloch states, showing that the band-edge spin splitting and spin polarization are encoded in a small number of symmetry-adapted spin-dependent hopping terms. We further analyze the accidental degeneracies of the effective Hamiltonian using screw eigenvalues and antiunitary operators. This analysis separates accidental degeneracies originating from the restricted term content of the effective Hamiltonian from degeneracies enforced by nonsymmorphic screw symmetries and time-reversal symmetry. The present model provides a symmetry-transparent starting point for understanding the band-edge electronic structure of chiral lead halide perovskites and for analyzing optical, spin, and transport responses in this class of materials.

We demonstrate that $k$-Markov sequences of unitary gates provide low-cost handles to manipulate the rate and structure of information spreading compared to traditional random, 0-Markov, circuits. For swap gates and brickwork circuits, we use graph cover time to demonstrate how $k$-Markov processes can be used to control operator transport. With swap gates and the set of Clifford gates that can change operator weight, we show how $k$-Markov sequences can be used to manipulate scrambling time and generate novel structures of spatial-temporal correlations across a qubit network. We show that $k$-Markov circuits constructed from pswap gates at fixed angle are equivalent to standard brickwork circuits with pswap angle drawn from nonuniform distributions generated by the $k$-Markov process. In those circuits, the time evolution of the average Hamming weight and the space-time correlation structure that remains after one-point quantities equilibrate again vary significantly from the 0-Markov case, depending on the transition probabilities of the process. More broadly, these results identify finite temporal memory as a control handle distinct from a circuit's degree of quantum chaos. For gate sets that fall short of volume-law scrambling, the equilibrium reached by one-point diagnostics is fixed by the gates alone, while the choice of $k$-Markov rule controls the approach to equilibrium and the structure of persistent, late-time correlations.

Thermal phonons in crystals are typically described in Fourier space, leaving open how disordered thermal vibrations are organized in real space-time. Recent work on two-dimensional crystals identified thermally excited vortical phonons—vorticity waves composed of traveling vortices with varying shapes and alternating-sign vorticity. Whether and how the dynamics of thermal vibrations can be organized by topological defects of vortex cores and saddles remain unclear. Here, using direct experiments on dusty plasma crystals and molecular-dynamics simulations of Yukawa crystals, we show that topological defects in the instantaneous velocity field organize thermally excited vortical phonons. In the Eulerian frame, slow-mode vorticity fluctuations are locally Gaussian yet develop coherent, intermittent, multiscale clusters of large vorticity-wave amplitude in space-time. In the Lagrangian frame, vortex cores display persistent superdiffusivelike transport together with concurrent evolution of core vorticity. Their kinetics obey robust topological rules, including charge-conserving pair creation and annihilation, exponential lifetime statistics, charge-dependent short-range correlations, and saddle-mediated splitting and merging of corotating vortices. These results move the description of thermal lattice vibrations beyond spectra alone and establish topological defects as organizing centers of thermally driven multiscale wave dynamics.

We show that low-frequency magnonic noise provides statistical fingerprints of nonlinear scattering-network configurations in a yttrium iron garnet waveguide. By tuning the magnetic field, we control whether three-magnon splitting and confluence are kinematically allowed and change the active scattering pathways. When three-magnon processes are allowed, the noise exhibits abrupt anomalies and distinct fluctuation classes, including random-telegraph and $1/f$-type spectra; otherwise, it approaches a near-white-noise form and evolves smoothly. Simulations support multistep magnon redistribution through competing nonlinear scattering pathways. Fluctuation statistics thus provide an experimental probe of dynamical-state selection in nonlinear magnon scattering networks.

Fluxonium superconducting qubits have demonstrated long coherence times and high single- and two-qubit gate fidelities, making them a favorable building block for superconducting quantum processors. We investigate the dominant limitations to fluxonium qubit energy relaxation time $T_1$ using a set of eight planar, aluminum-on-silicon qubits. We find that a circuit-based model for capacitive dielectric loss best captures the frequency dependence of $T_1$, which we analyze within both a two-level and a six-level energy relaxation model. We convert the measured $T_1$ into an effective capacitive quality factor $Q_{\mathrm{C}}^{\mathrm{eff}}$ to compare qubits on equal footing, accounting for independently estimated contributions from $1/f$ flux noise and radiative loss to the control and readout circuitry. We apply this methodology to compare qubits from two fabrication processes: a baseline process and one that applies a fluorine-based wet treatment prior to Josephson junction deposition. We resolve a small improvement of 13.8% $\pm 8.4\%$ in the process mean $Q_{\mathrm{C}}^{\mathrm{eff}}$, indicating that the fluorine treatment may have reduced loss from the metal-substrate interface, but did not address the primary source of loss in these fluxonium qubits.

Nonlocal crystals are systems with translational symmetry but arbitrary-range couplings or interactions between degrees of freedom. We argue that such systems can realize symmetry-allowed but locality-forbidden ground-state symmetry eigenvalues. This is demonstrated by constructing an exactly solvable fermionic model in a one-dimensional translationally invariant setting in symmetry class AII with inversion symmetry, using a Hatsugai-Kohmoto-type model. The resulting unique gapped ground state exhibits the size-independent inversion eigenvalue $-1$, which is allowed from the fixed-size zero-dimensional viewpoint but forbidden in both noninteracting band insulators and local crystalline fermionic symmetry-protected topological phases. Our work establishes Hatsugai-Kohmoto-type nonlocality as a concrete route to realizing symmetry sectors that are inaccessible in such local phases.

We report direct measurements of magnetically inhibited heat transport in an underdense laser-produced plasma subjected to externally applied magnetic fields of up to 20 T. Spatially and temporally resolved Thomson-scattering data show that the peak electron temperature increases by a factor $\sim 1.4$ relative to the unmagnetized case, as cross-field thermal conduction is maximally suppressed. This state is observed for $B\ge 10$ T and is sustained over $\sim 0.5 \text{ns}$. The subsequent temperature decrease is primarily driven by a reduction in inverse-bremsstrahlung heating as the electron density cavitates. Our experimental results are consistent with simple analytical estimates and are corroborated by Vlasov-Fokker-Planck simulations, suggesting that the plasma reaches the maximum temperature gain for an electron Hall parameter ${\chi }_{\text{Hall}}\gtrsim 50$ ($T_e\sim 800 \text{eV}, n_e\sim 3\times {10}^{19} {\text{cm}}^{-3}$). These findings demonstrate that effective magnetothermal insulation can occur in magnetized inertial confinement fusion schemes without the need for extremely large magnetic fields.

Recent studies have shown that novel collective behaviors emerge in complex systems due to higher-order interactions. However, the way in which the structural correlations of these interactions shape such behaviors remains a significant gap in current research. To address this, we use signatures of higher-order behaviors (HOBs) to identify the underlying dynamical rules, or higher-order mechanisms (HOMs). In this work, we compare several HOB measures derived from information theory. Utilizing a simplicial susceptible-infected-susceptible contagion model, we demonstrate that simpler, computationally efficient measures can serve as robust indicators of HOMs. We uncover the phenomenon of cross-order induced behaviors, where behavioral signatures emerge at interaction orders where no direct mechanism is present. Crucially, these cross-order HOBs are not simply induced by structural correlations—such as nestedness and hyperedge overlap—but they appear in the neighborhood of any HOM. Among the information-theoretic measures we tested, synergy is the most reliable indicator of the true order where the underlying mechanism is at play. These findings offer new insights into the relationship between the network structure and observed dynamics of higher-order systems.

Symmetric mass generation is the interaction-induced opening of a fermion gap without spontaneous symmetry breaking. The anomaly-free 3–4–5–0 model of Wang and Wen provides a minimal one-dimensional setting for this phenomenon, but a direct lattice realization faces two obstacles: fermion doubling for local chiral discretizations and perturbative irrelevance of the six-fermion gapping interaction. We address both obstacles. First, we formulate the model on a strictly one-dimensional tangent-fermion lattice, where a nonlocal hopping produces a single chiral branch without a mirror partner while retaining an efficient tensor-network representation. Second, we add a Hubbard-type density-density interaction (Luttinger parameter $K$) that reduces the scaling dimension of the 3–4–5–0 interaction from 5 to $5K$, making it relevant for $K<2/5$. Density-matrix renormalization group calculations show the opening of an excitation gap in this regime without the appearance of a degenerate ground state, the hallmark of symmetric mass generation.

Identifying the regions responsible for plastic flow in amorphous solids remains an open problem, since structural disorder seems to prevent the direct application of concepts such as dislocations, topological defects that successfully describe irreversible deformations in crystalline systems. Here, we introduce fields of dislocation, disclination, and incompatibility densities, which in crystals reduce to the standard sources of plasticity, and assess their predictive power in amorphous materials. We find that, in a simulated two-dimensional glass as well as in two- and three-dimensional experimental granular systems, these fields exhibit strong spatial correlations with $D_{\text{min}}^2$, a standard descriptor used to locate plastic events in disordered solids under shear, indicating that these fields are indeed reliable quantities for predicting plastic events. In contrast to $D_{\min }^2$, these fields provide deeper insight into how local rotational and translational motions become coupled well before the onset of plastic events. Moreover, by allowing the two contributions to be disentangled, they reveal that rotational defects become increasingly dominant in three dimensions. Our approach paves the way for describing plasticity in crystalline and amorphous solids in a unified manner.

We introduce the subdimensional entanglement entropy (SEE), defined on subdimensional entanglement subsystems (SESs) embedded in the bulk, as an entanglement-based probe of how geometry and topology jointly shape universal properties of quantum matter. By varying the dimension, geometry, and topology of the SES, we show that the subleading term of SEE exhibits sharply distinct responses in a series of stabilizer states representing fixed points of different phases, including cluster states, ${\mathbb{Z}}_q$ topological orders, and fracton orders. Treating the reduced density matrix of an SES as a many-body mixed state supported on the SES manifold, we further establish a general correspondence between bulk stabilizers and mixed-state symmetries on SESs, separating them into strong and weak classes, and use it to identify strong-to-weak spontaneous symmetry breaking within SESs. Finally, for SESs with nontrivial SEE, we show that a set of weak symmetries acts as transparent patch operators of the corresponding strong symmetries. This motivates the notion of transparent composite symmetry, which remains robust under bipartition-factorized finite-depth quantum circuits that preserve SEE, and implies that a $D$-dimensional SES may holographically encode a $(D+1)$-dimensional topological order. These results establish SEE not only as a sharp probe of geometric-topological response, but also as a route from bulk pure-state entanglement to mixed-state symmetry and holography on subdimensional manifolds.

Symmetry plays a central role in determining the electronic structure and topology of nodal-line semimetals. ${\text{SrAl}}_4$ is a nodal-line semimetal with tetragonal $I4/mmm$ symmetry at room temperature, an incommensurate charge-density-wave transition at $T_{\mathrm{CDW}}\simeq 240\mathrm{K}$ accompanied by $C_4$ symmetry breaking, and a low-temperature monoclinic transition near $T\simeq 90\mathrm{K}$. Here, we use nonlinear optical second- and third-harmonic generation to track the evolution of crystal symmetries in ${\text{SrAl}}_4$ with temperature and disorder. Temperature-dependent second-harmonic generation uncovers strong coupling between the lattice and the charge-density-wave order and shows that disorder quenches the low-temperature monoclinic phase. Room-temperature third-harmonic generation reveals broken $C_4$ rotational symmetry in contrast to the reported tetragonal bulk structure, possibly due to a symmetry-lowered surface reconstruction. These results establish nonlinear harmonic generation as a sensitive probe of intertwined bulk and surface symmetry breaking in ${\text{SrAl}}_4$ and as a complementary tool for refining symmetries where space group assignment through diffraction is ambiguous.

Understanding ultrafast ionization dynamics in high-density plasmas is essential for applications such as particle acceleration, short-pulse x-ray generation, and laser fusion. However, resolving ionization states inside optically opaque plasmas with femtosecond resolution remains challenging. Using femtosecond-resolved x-ray absorption spectroscopy, we directly measured inner-shell vacancies, overall charge states, and the nonthermal electron population responsible for ionization in solid-density copper plasma. In copper plasma generated by a 40-fs relativistic laser pulse, ionization proceeds within 0.5 ps. M- and outer-shell ionization persist for over 10 ps, whereas L-shell vacancies decay within 4 ps. The population of electrons capable of L-shell ionization decreases in picoseconds, in agreement with particle-in-cell simulations incorporating atomic processes. Our spectroscopic approach provides direct experimental insights into ultrafast ionization dynamics in high-density plasmas, supporting improvements in the modeling of laser-driven plasmas.

We propose and simulate a laboratory platform to study the effects of positrons in magnetic reconnection using laser-driven capacitor coils. Using particle-in-cell simulations, we show that externally injected MeV electron-positron pairs are trapped in the coil current sheet, significantly modifying the reconnection dynamics and particle acceleration. These pairs increase the reconnection rate by a factor of approximately 8, which Ohm's law decomposition reveals to be driven by the divergence of the generalized pressure tensor. Based on their high energy and magnetization, the pairs also substantially broaden the diffusion region. Particle tracking simulations in realistic coil magnetic fields further demonstrate that injected pairs can remain confined for several picoseconds, providing conditions for sustained interaction with the reconnection region. These results establish a near-term pathway to first laboratory studies of positron-influenced reconnection, bridging high-energy-density experiments with pair-dominated astrophysical environments.

Vacuum fluctuations in quantum field theory impose fundamental limitations on our ability to measure time at arbitrarily short scales. To investigate the impact of universal quantum field theory effects on observer-dependent time measurements, we introduce a clock model based on the vacuum decay probability of a finite-sized quantum system. This model defines an effective notion of proper time that depends on the microscopic properties of the clock and on how it samples vacuum fluctuations along its trajectory. We show that, in the long-time regime, this notion of time reduces to the usual proper time of special relativity. However, by studying a microscopic twin-paradox scenario, we find that, in general, time is not determined solely by the trajectory connecting two events, but also by how vacuum fluctuations interact with the internal structure of the clocks.

The advent of quantum computing necessitates the transition of worldwide cryptosystems to postquantum cryptography (PQC), which is founded upon the problem of finding short vectors in high-dimensional structured lattices. It is assumed that the structure of these lattices cannot be exploited by quantum or classical algorithms attempting to find short vectors. In this work, we focus on the structure of the lattices used in PQC protocols—negacyclic (and cyclic) lattices—and provide a quantum algorithmic framework that efficiently encodes the structured lattices into Hamiltonians by exploiting their underlying symmetries. The efficient encoding substantially reduces the dimension of the corresponding Hilbert space by limiting it to a relevant subspace where short vectors are likely to be found—leading to significant savings in quantum resources (e.g., qubit count and circuit depth) required to implement a quantum algorithm for finding short vectors. We analytically prove the efficient encoding procedure and benchmark the proposed framework using the variational quantum eigensolver, demonstrating improved results with reduced quantum resources.

In this work, we present numerical evidence for the spontaneous breaking of a continuous $U\left(1\right)$ symmetry in a nearest-neighbor interacting spin-1 chain at a quantum critical point separating two XY quasi-long-range ordered phases distinguished by a spontaneously broken ${\mathbb{Z}}_2$ symmetry. Remarkably, the continuous symmetry breaking emerges precisely at the critical point of the discrete order parameter, suggesting a mechanism beyond currently established scenarios. At criticality, the XY correlations develop true long-range order, accompanied by a finite perpendicular magnetization, a zero-frequency Bragg peak in the transverse dynamical structure factor, and sharp gapless collective excitations. From complementary static and dynamical observables, we quantitatively determine the critical exponents, obtaining a dynamical exponent $z=1.50\pm 0.04$ and an anomalous dimension $\eta =1.04\pm 0.03$. Remarkably, the value of $z$ coincides with the one-dimensional Kardar-Parisi-Zhang exponent despite the system being an equilibrium quantum many-body system. We further show that the noninteracting continuum limit is equivalent to the recently introduced transverse quantum fluid, displaying their off-diagonal long-ranged order in one dimension. Complementing the numerical study, we derive the renormalization-group flow equations of the continuum theory to second order in the $\varepsilon$ expansion. We identify an interacting fixed point whose critical behavior differs from the Ising universality class already at two-loop order, although the perturbative exponents remain far from the numerical values.