Superconducting (SC) pairing mechanism, origin of high $T_c$, and symmetry of SC order parameter in Fe-based superconductors are among the important unsolved problems in condensed matter and materials physics. We study the SC properties of ThFeAsN, an Fe-based high-$T_c$ superconductor, by ab initio superconducting density functional theory calculations with electron-phonon coupling, screened static and dynamic electron-electron Coulomb repulsion, and spin fluctuation (SF)-mediated pair interaction fully taken into account. Our calculations reveal that ThFeAsN is an SF-mediated multiband superconductor with the calculated $T_c$ of 22.4 K and the $d_{xy}$-wave SC order parameter with different signs on different Fermi surface sheets, consistent with most experiments. We also present distinct SC properties such as quasiparticle density of states and ultrasonic attenuation coefficient, which can be immediately verified by experiments.

We present a hardware-native gadget framework for solving constraint-satisfaction problems on Rydberg quantum computing architectures. Our approach introduces a compact ${\text{xor}}_1$ gadget that enforces exactly-one constraints, ubiquitous in combinatorial optimization, directly through geometric embedding and blockade interactions. A key advantage of the ${\text{xor}}_1$ gadget is its fixed, problem-size-independent detuning requirements: Enforcing constraints through blockade interactions eliminates the need for large penalty terms, thereby substantially reducing the detuning range compared to quadratic unconstrained binary optimization (QUBO) formulations and improving experimental feasibility. By tailoring the construction to the geometric connectivity of Rydberg-atom arrays, the framework bypasses the all-to-all physical couplings often assumed in logical encodings. This enables embeddings compatible with planar layouts and avoids highly connected arrangements. We develop scalable implementations that reduce atom count and connectivity overhead while avoiding extensive classical preprocessing, making them compatible with near-term neutral-atom hardware. As illustrations, we apply our framework to the gate-assignment and $N$-queen problems, highlighting its practicality, resource efficiency, and hardware compatibility. In these examples, we observe reductions in detuning range of up to $99\%$ and savings in atom count and connectivity overhead of up to $54\%$ compared to the QUBO method. These results establish a route toward implementing large-scale combinatorial optimization on Rydberg platforms beyond the limits of existing encodings.

Remote synchronization, in which indirectly connected nodes synchronize while the mediating hub remains desynchronized, is a counterintuitive form of collective dynamics in complex networks. Most previous studies have treated each node as a single oscillator, whereas nodes in realistic systems often represent populations of interacting dynamical units. Here, we study remote synchronization in a star network whose nodes are Kuramoto oscillator populations. Each node contains many internally coupled oscillators with coupling strength $K$, and different nodes interact through an internode coupling strength $L$. We show that remote synchronization emerges only at an intermediate level of internal synchrony: The leaf nodes become strongly synchronized with each other, while the hub remains weakly synchronized with them, when the internal order parameter is neither close to zero nor close to one. Increasing $K$ further causes an abrupt breakdown of the remote-synchronized state. Detrended fluctuation analysis reveals enhanced scaling behavior and critical-like long-range temporal correlations near this breakdown boundary. A two-parameter scan in the $(L,K)$ plane confirms that the remote-synchronized regime occupies a finite region associated with intermediate internal order and relatively low detrended fluctuation analysis exponent. We further provide a phenomenological effective-phase interpretation, showing that internal coupling controls the coherence, susceptibility, and stability of each oscillator population. These results demonstrate that internal population dynamics can regulate both the emergence and critical-like breakdown of remote synchronization.

Earthquake diffusion is commonly interpreted either as the migration of fluids or as the propagation of triggering cascades within branching processes. In the latter framework, anomalous diffusion emerges naturally from the long-memory kernels of epidemic-type aftershock sequence (ETAS) models. Here, we introduce a swarm-informed ETAS (SIETAS) model designed to describe volcanic seismic swarms. The model combines a temporally truncated power-law triggering kernel with a spatially localized logistic kernel, thereby introducing intrinsic temporal and spatial scales into the triggering process. Using an AI earthquake catalog from the ongoing Campi Flegrei unrest, we show that SIETAS provides a substantially better description of seismicity than the standard ETAS formulation. We further demonstrate that earthquake diffusion exhibits clear multiscaling behavior characterized by three effective scaling regimes. Analytical arguments based on branching-process theory and continuous-time random walks indicate that the SIETAS kernels generate a crossover from transient anomalous diffusion to an effectively normal-diffusive regime, followed by saturation due to finite subcriticality. We discuss how the observed multiscaling behavior may emerge from the interplay between short-time triggering, finite temporal memory, finite spatial localization, and secondary components of the triggering kernel. These results establish a connection between swarm-informed earthquake triggering and multiscale diffusion phenomena in volcanic environments.

Gaussian baths are widely used to model non-Markovian environments, yet the cost of accurate simulation at long times remains poorly understood, especially when spectral densities exhibit nonanalytic behavior as in a range of realistic models. We rigorously bound the complexity of representing bath correlation functions on a time interval $[0,T]$ by sums of complex exponentials, as employed in recent variants of pseudomode and hierarchical equations of motion methods. These bounds make explicit the dependence on the maximal simulation time $T$, inverse temperature $\beta$, and the type and strength of singularities in an effective spectral density. For a broad class of spectral densities, the required number of exponentials is bounded independently of $T$, achieving time-uniform complexity. The $T$ dependence emerges only as polylogarithmic factors for spectral densities with strong singularities, such as step discontinuities and inverse power-law divergences. The temperature dependence is mild for bosonic environments and disappears entirely for fermionic environments. Thus, the main bottleneck for long-time simulation is the presence of sharp nonanalytic features in the bath spectrum. Our results are instructive both for long-time simulation of non-Markovian open quantum systems and for Markovian embeddings of classical generalized Langevin equations with memory kernels.

Dynamical instabilities can amplify small perturbations into measurable signals, offering a route to quantum-enhanced sensing. This mechanism was experimentally demonstrated in a collective spin system with quadratic interactions, described by a twist-and-turn Hamiltonian, where quantum evolution near an unstable point leads to exponential growth of spin fluctuations, enabling metrological gain beyond the standard quantum limit. Here, we show that a quartic extension of this Hamiltonian substantially increases the amplification. This additional nonlinear term reshapes the phase-space structure, generating new unstable fixed points with larger local Lyapunov exponents and therefore faster signal amplification at shorter evolution times. Remarkably, even for the same instability rate (equal Lyapunov exponent), collective multibody interactions outperform the quadratic case, demonstrating that metrological gain is not determined by the Lyapunov exponent alone. We show analytically that the finite-time growth of the gain is governed also by the local phase-space curvature around the unstable point. Only for a symmetric unstable point, as in the quadratic case, is the finite-time gain described by the Lyapunov exponent alone. Our results identify local phase-space curvature as an additional resource for optimizing the speed and performance of quantum sensors.

Bubble-shaped Bose-Einstein condensates (BECs) constitute a unique class of quantum fluids with a hollow, thin-shell geometry that supports a wide variety of phenomena distinct from those of compact condensates. Numerical simulation of such systems is particularly challenging due to their inherently three-dimensional structure and extreme aspect ratios. We present an efficient finite-difference simulation framework for solving partial differential equations in nontrivial topologies, with a focus on the static and dynamical modeling of bubble-shaped BECs. By employing selective spatial sampling on a semistructured grid, our method substantially reduces memory usage and achieves more than an order-of-magnitude improvement in computational performance compared with conventional split-step Fourier solvers. The algorithm is naturally extendable to highly parallel execution on graphics processing units (GPUs), enabling large-scale, time-dependent simulations of thin-shell condensates. We apply this framework to simulate the formation of bubble BECs through a controlled hollowing-out protocol using ab initio trapping potentials relevant to the Cold Atom Laboratory aboard the International Space Station. From these simulations, we identify characteristic timescales and parameter ramps required to achieve adiabatic evolution, thereby assessing the feasibility of experimentally realizing bubble-shaped condensates in microgravity environments.

Since the discovery of charge density wave (CDW) and superconductivity, kagome metal ${\mathrm{AV}}_3{\mathrm{Sb}}_5$ ($\mathrm{A}=\mathrm{K}$, Rb, Cs) provides a new platform for exploring novel many-body quantum phenomena. In ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$, a stripelike CDW with commensurate wave vector $q=3/8$ was observed under moderate pressures, which leads to a peculiar superconducting double-dome behavior in pressure-dependent phase diagram. Previous density functional theory (DFT) calculations indicate that the pressure-induced stripelike CDW is beyond conventional phonon softening scenario, suggesting a nontrivial role of electronic correlations. However, an in-depth understanding for the pressure-induced unconventional CDW remains elusive. Here, we performed pressure-dependent ${}^{51}\mathrm{V}$ nuclear magnetic resonance (NMR) measurements on ${\mathrm{KV}}_3{\mathrm{Sb}}_5$ and ${\mathrm{RbV}}_3{\mathrm{Sb}}_5$. Although the superconducting double-dome behavior is absent in pressurized ${\mathrm{KV}}_3{\mathrm{Sb}}_5$ and ${\mathrm{RbV}}_3{\mathrm{Sb}}_5$, a pressure-induced CDW phase, ascribed to a possible incommensurate triple-$Q$ CDW, is identified by NMR spectra in both materials, indicating that the pressure-induced unconventional CDW beyond DFT calculations is a common feature for kagome metal ${\mathrm{AV}}_3{\mathrm{Sb}}_5$. In contrast to the stripelike CDW, the pressure-induced incommensurate triple-$Q$ CDW does not strongly suppress the superconducting temperature ($T_{\mathit{c}}$) but coincides with an almost plateau behavior at intermediate pressure regime in the pressure-dependent superconducting phase diagram. Furthermore, by systematically analyzing the Korringa relation between Knight shift and nuclear spin-lattice relaxation rate in ${\mathrm{AV}}_3{\mathrm{Sb}}_5$, Van Hove singularity-driven electronic fluctuations are revealed as an effective knob for the pressure-induced unconventional CDW. Finally, our present findings underscore the pressure-induced unconventional CDW as a novel correlated quantum state in kagome metal ${\mathrm{AV}}_3{\mathrm{Sb}}_5$.

Recent experiments [Phys. Rev. B 109, 245123 (2024)] revealed striking inverse-current ($1/I$) quantum oscillations in quasi-one-dimensional charge-density-wave (CDW) insulators and proposed an intrinsic Floquet sideband mechanism arising from the sliding condensate. Here, we develop the complete theoretical framework underlying this proposal. We provide an exact Floquet diagonalization of the uniformly sliding CDW problem, yielding split gap edges and a ladder of Floquet sidebands with explicit unitary transformation and spectral functions. Using this exact solution, we formulate weak-probe tunneling spectroscopy and demonstrate that the local Floquet spectrum naturally yields $1/I$ oscillations as successive sideband edges cross a fixed contact chemical potential. The measured period fixes $N_{\mathrm{eff}}\epsilon \simeq 4.80\mathrm{eV}$, where $\epsilon$ is the local contact-to-gap-edge offset. Combining this relation with the experimentally resolved low-temperature oscillations constrains the effective coherent channel count to be at most of order ${10}^3$, far below the geometric estimate $N_{\mathrm{geom}}\sim 3\times {10}^4$, while $\epsilon =10\mathrm{meV}$ gives the representative value $N_{\mathrm{eff}}\simeq 480$. This reduced coherent scale is naturally realized by a spatially nonuniform percolating network, but does not require $N_{\mathrm{eff}}$ independent end-to-end wires. Furthermore, using a segmented multiterminal model, we show that inelastic phase-slip dephasing near the contacts explains the experimentally observed suppression of oscillation visibility on outer voltage probes. Finally, we contrast the persistent-current-driven multiterminal geometry with a homogeneous voltage-biased two-terminal reference calculation. Our results establish a nonequilibrium transport framework for the observed $1/I$ oscillations and identify an observability condition in which the Floquet spacing must exceed collective and quasiparticle broadening.

Human behaviors, particularly nonpharmaceutical interventions (NPIs), are dynamically coupled with epidemic spreading. However, most models assume a linear relationship between perceived risk and infection rates, failing to capture the nonlinear nature of real-world behavioral responses. Here, we propose a behavioral epidemic model by incorporating nonlinear feedback and social influence, and analytically derive its critical thresholds. Notably, once the infection rate exceeds a critical threshold, the fraction of NPI adopters abruptly drops to zero, in contrast to classic findings in linear models. This paradoxical decline indicates a social dilemma: While abandoning NPIs is individually optimal at high infection rates, it collectively triggers an explosive epidemic surge. Furthermore, as the intensity of social influence increases, the system undergoes a Hopf bifurcation leading to periodic oscillations, which reflects a vicious cycle of recurrent epidemic waves. Finally, we confirm the robustness of this NPI-abandonment dilemma in networked populations. Our work illustrates rich emergent dynamics, challenging traditional perspectives on behavioral epidemiology.

We introduce a two-dimensional model of spin-$1/2$ Dirac fermions in graphene subjected to a highly tunable electric field, which exhibits super-Klein tunneling. The electric field can be continuously interpolated between two limiting configurations: a uniform electrostatic Lorentzian barrier with translational invariance and a chain of well-separated electrostatic scatterers. We demonstrate that super-Klein tunneling arises naturally as a direct consequence of the intrinsic connection of the model to free-particle dynamics, a relation that is established through methods of supersymmetric quantum mechanics, which provide an elegant and analytically tractable framework. Besides the mentioned super-Klein tunneling, scale invariance of the model and invisibility of the potential for particles of specific energy are revealed, and possible routes toward experimental realization are discussed.

We study a ${\mathbb{Z}}_3$-symmetric Rabi model that describes a three-level system coupled to two bosonic modes. We derive a mapping of the two-mode ${\mathbb{Z}}_3$ Rabi model onto a qubit-boson ring. This mapping allows us to formulate a realistic implementation of the ${\mathbb{Z}}_3$ Rabi model based on superconducting qubits. It also provides context for the previously proposed optomechanical implementation of the ${\mathbb{Z}}_3$ Rabi model. In addition, we propose a physical implementation of the ${\mathbb{Z}}_3$ Potts model via a coupled chain of ${\mathbb{Z}}_3$ Rabi models.

We present a technique to observe the optical manipulation of individual quantum states of ${\mathrm{H}}_3^{+}$ ions stored inside a heavy-ion storage ring, where the excitation is detected by electron-beam-assisted action spectroscopy. The transitions addressed here are chosen to enable multicolor spectroscopy of states far above the energetic barrier, where this molecule—with a triangular ground state—can sample linear geometries. This region of the spectrum has so far been inaccessible due to extremely weak direct transition strengths from the ground vibrational level. Our experiments pave the way for spectroscopy of the simplest polyatomic molecule in a previously unexplored energetic territory, which would benchmark theoretical data crucial for the understanding of this fundamental molecular system. Our results also demonstrate laser pumping to vibrationally and rotationally excited states of ${\mathrm{H}}_3^{+}$, gaining model-dependent access to their relative dissociative electron recombination rates.

The emerging field of quantum magnonics seeks to understand and harness the quantum properties of magnons—quantized collective spin excitations in magnets. Squeezed magnon states arise naturally as the equilibrium ground states of anisotropic ferromagnets and antiferromagnets, representing an important class of nonclassical magnon states. In this work, we show how a qubit-conditioned quantum quench of an anisotropic ferromagnet can be used for Heisenberg-limited parameter estimation based on measurements of the qubit only. In the presence of ground-state squeezing, the protocol yields information about the eigenmode frequency of the coupled magnon-qubit system, whereas no information is gained in the absence of such squeezing. The protocol therefore leverages genuine quantum correlations in the form of magnonic squeezing while simultaneously relying on the equilibrium character of this squeezing—a feature distinctive to magnetic systems.

Spin shuttling has crystalized as a powerful and promising tool for establishing intermediate-range connectivity in semiconductor spin-qubit devices. Although experimental demonstrations have performed exceptionally well on different materials platforms, the question of how to handle areas of low valley splitting in silicon during shuttling remains unresolved. In this work, we explore the possibility of utilizing the valley degree of freedom, particularly in regions of low valley splitting, to allow mobile spin qubits to be shuttled through an occupied stationary quantum dot, thereby leapfrogging over the stationary electron. This not only grants a more enriched mobility for shuttled electrons, as it opens new possible routing paths, but also enables the implementation of an entangling swap${}^{\gamma }$ two-qubit gate operation in the process. Simulating this process for different sets of parameters, we demonstrate the feasibility of such an operation and offer a unique use case for otherwise precarious regions of a quantum processor chip and propose a possible extension to the set of possible operations for silicon spin-qubit devices.

We numerically investigate how particle surface roughness affects the static and dynamic properties of a hard-particle fluid across a wide range of densities, $\rho$. These simulations of a simple model of granular systems reveal that, although the amplitude and coverage of surface corrugation significantly influence the $\rho$ dependence of system properties, the qualitative behavior of this dependence remains unchanged. These findings can be described quantitatively by introducing an effective particle size, which enables a direct mapping of the rough particle systems to equivalent hard-disk systems. Analytical calculations provide an explicit form of this mapping and allow us to predict the static and dynamic properties of rough particles using standard liquid-state theories for hard disks.

An avoided crossing is a familiar spectral signature of interaction between nearby modes, but the eigenvalue trajectory alone does not establish whether their modal identities are exchanged. We examine this question in a deformed microwave billiard by comparing finite element eigenvalues and fields. Across 21 screened adjacent level events, the spectral slope is compared with the boundary response obtained from the fields at the event center. For the 11 events whose rotation width can be resolved within the sampled interval, the boundary-derived and overlap-derived widths agree to within about 11%. One event behaves differently: The spectral model predicts substantial modal rotation, while the computed fields change very little and are instead reproduced by the boundary response. Another event shows that the mode that improves the eigenvalue model is not the mode that best restores the field subspace. Spectral repulsion alone is therefore not sufficient to determine modal exchange or the reference subspace required over a finite parameter range.