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.

Fluid equations are nonlinear, dissipative, and non-Hamiltonian, which makes their relation to Schrödinger evolution and quantum algorithms nontrivial. We derive an exact Eulerian Cole-Hopf-type reformulation of isothermal compressible Navier-Stokes (NS) flow in Schrödinger-type amplitude variables. To our knowledge, this gives the first exact Cole-Hopf-type Schrödinger-variable reformulation of compressible NS flow. In two dimensions, a Helmholtz decomposition separates the velocity into compressive and vortical potentials, whose logarithmic transforms yield two scalar imaginary-time Schrödinger-type equations with nonlinear self-consistent potentials. We show that the mixed density-compressive amplitude ${\mathrm{\Psi }}_{\alpha }={\rho }^{\alpha }{\mathrm{\Theta }}^{1-2\alpha }$, where $\rho$ is the density, $\mathrm{\Theta }$ is the compressive amplitude, and $\alpha \ne 0,1/2$, satisfies a nonlinear Schrödinger-type equation with a vector-potential-coupled Laplacian. The transformed system is exactly equivalent to compressible NS and is nonlocal only through Helmholtz and Poisson projections. In three dimensions, the density-carrying equation retains the same vector-potential-coupled structure, while the solenoidal sector admits a compressible analog of Ohkitani’s [Phys. Rev. E 92, 033010 (2015)] incompressible NS Cole-Hopf formulation. Unlike unitary hydrodynamic Schrödinger-flow representations, the present equations are imaginary-time heat or drift-diffusion equations with self-consistent potentials, but they remain an exact change of variables for compressible NS. A two-dimensional Kelvin-Helmholtz shear-layer calculation verifies the transformed equations against a direct compressible NS simulation. The formulation exposes operator structures that may be useful for reduced flow descriptions, quantum algorithms for operator evolution, and quantum partial differential equation solvers.

Material defects give rise to parasitic two-level systems (TLS) that present a major source of decoherence in superconducting qubits. Here, we study a strongly coupled TLS that resides in the tunnel barrier of transmon qubit. We use multiphoton spectroscopy and TLS strain tuning to explore the rich spectrum of the interacting three-partite system consisting of TLS, qubit, and its readout resonator. This reveals a strong effective resonant coupling between the TLS and the qubit's readout resonator, which dresses the resonator states and results in a resonance frequency shift that spoils the readout signal. Our finding presents yet another way how material defects can interfere with qubit operation and hinder the realization of solid-state quantum processors.

Drawing inspiration from swarm intelligence, we show that short-range attractive interactions between thermally driven Brownian quasiparticles enable energy-efficient optimization. As quasiparticles can be generated directly within a material, the swarm size can be adjusted with minimal energy overhead. Using an optimization task defined by a spatially varying temperature landscape, we quantitatively show that interacting swarms reliably identify global optima and significantly outperform noninteracting searchers within a well-defined regime of interaction strength and swarm size. This improvement arises from emergent cooperative behavior, where local interactions guide the swarm toward high-quality solutions without central coordination. To link our physical model to experimental realizations, we coarse grain the quasiparticle dynamics onto a sensor lattice and generate trajectories emulating particle-tracking measurements. We further show that the interacting swarm adapts robustly to landscapes that evolve over time. These findings establish interacting Brownian quasiparticles as a physical platform for scalable and energy-efficient unconventional computing.

Code switching offers a route to universal, fault-tolerant quantum computation by circumventing the limitation implied by the Eastin-Knill theorem against a universal transversal gate set within a single quantum code. Here, we present a fault-tolerant code-switching protocol between two versions of the $\left[\right[8,3,2\left]\right]$ code. One version supports weakly fault-tolerant single-qubit Clifford gates, while the other supports a logical $\overline{\mathrm{CCZ}}$ gate via transversal $T/T^{†}$ together with logical $\overline{\mathrm{CZ}}$, $\overline{\mathrm{CNOT}}$, and $\overline{\mathrm{SWAP}}$ gates. Because both codes have distance 2, the protocol operates in a postselected, error-detecting regime: Single faults lead to detectable outcomes, and accepted runs exhibit quadratic suppression of logical error rates. This yields a universal scheme for postselected fault-tolerant computation. We validate the protocol numerically through simulations of state preparation, interblock logical teleportation, code switching, and a three-logical-qubit implementation of Grover's search.

Quantum resource theories identify the features of quantum computers that provide their computational advantage over classical systems. We investigate the resources driving the complexity of classical simulation in the standard model of continuous-variable quantum computing, and their interplay enabling computational universality. Specifically, we uncover a new property in continuous-variable circuits, analogous to coherence in discrete-variable systems, termed symplectic coherence, defined as the ability of Gaussian gates to mix position and momentum operators. Using quadrature propagation across multiple computational paths, we develop an efficient classical simulation algorithm for continuous-variable computations with symplectic coherence constant in the size of the circuit. This establishes symplectic coherence as a necessary resource for universality in continuous-variable quantum computing, alongside non-Gaussianity and entanglement. Via the Gottesman-Kitaev-Preskill encoding, we show that the interplay of these three continuous-variable quantum resources mirrors the discrete-variable relationship between coherence, magic, and entanglement.

Feedback-based quantum algorithms (FQAs) operate by iteratively growing a quantum circuit to optimize a given task. At each step, feedback from qubit measurements is used to inform the next quantum circuit update. In practice, the sampling cost associated with these measurements can be significant. Here, we ask whether FQA parameter sequences can be predicted using classical machine learning, obviating the need for qubit measurements altogether. To this end, we train a teacher-student model to map problem instances to associated FQA parameter curves in a single classical inference step. We first study weighted MaxCut problem instances, where numerical experiments show that this machine learning model can accurately predict FQA parameter curves across a range of problem sizes, including sizes not seen during model training. We then extend the analysis to transverse-field Ising models on graphs and analyze how this learning strategy performs and generalizes beyond the original MaxCut setting. To evaluate performance, we compare the predicted parameter curves in simulation against FQA reference curves and linear quantum annealing schedules. We observe similar results to the former and performance improvements over the latter. These results suggest that machine learning can offer a heuristic, practical path to reducing sampling costs and resource overheads in quantum algorithms.

The Ti $L_{2,3}\text{−}\mathrm{edge}$ x-ray absorption spectra of various titanium oxides, including perovskite $\mathrm{SrTi}{\mathrm{O}}_3$, rutile and anatase $\mathrm{Ti}{\mathrm{O}}_2$, and ilmenite $\mathrm{CoTi}{\mathrm{O}}_3$, are analyzed with particular attention to the energy range beyond the near-edge/charge-transfer region and up to the oxygen $K$ edge. We found that the spectral structure varies among materials and can be described using density functional theory without including the multielectron effects indispensable for describing near-edge and charge-transfer structures. We term the structures in this energy range the middle-range-energy structure and show that the distinct features are determined by the local atomic geometry around the target Ti atoms and, essentially, by the partial density of states of those atoms. Here, we demonstrate how to extract information from middle-range-energy structures by comparing them with ab initio calculations, and we propose this energy-range analysis as a new method for studying local atomic geometry, free of parameters describing multielectron effects.