With the growing demand for the high-intensity hadron beams in various applications in recent years, coherent beam instabilities driven by space charge are of critical concern for those high-intensity hadron accelerator projects, where the plasma dynamics of beams is pronounced and requires careful consideration. In this paper, an analytical model is developed to characterize coherent beam instabilities in circular machines. Based on the proposed model, a coherent mode, namely the vertical coupled mode, is identified. It is demonstrated that the tilting instability is more enhanced in circular machines because of the increased anisotropy from dispersion. Moreover, the well-known envelope instability in linear accelerator can be generalized and classified into “a family of envelope instabilities” for high-intensity circular accelerators. The proposed analytical model has been compared to particle-in-cell simulations and shows good agreement. The chart of the envelope instability family can be adopted for optimization of the working point to achieve higher beam intensity.

Numerous experiments have shown that $\alpha \text{−}\mathrm{RuC}{\mathrm{l}}_3$ exhibits a spin liquid (SL) state near 7.1 T when an in-plane magnetic field is applied perpendicular to the Ru-Ru bond directions ([110]), while SL states are rarely observed under fields applied along the Ru-Ru bond ([100]). The underlying mechanism for this pronounced anisotropy remains elusive. In this work, we employ semiclassical spin dynamics simulations to investigate the magnetization evolution of $\alpha \text{−}\mathrm{RuC}{\mathrm{l}}_3$ with lattice distortion under varying external magnetic fields. It is found that each [100] direction has its own dominant orientation, and each [110] orientation marks the boundary, where the two alignments compete with each other. The magnetizations are influenced by multiple interactions and perturbations from lattice distortions, leading to the occurrence of the SL state in the [110] direction. These results provide new insights into the field-induced phase transitions in $\alpha \text{−}\mathrm{RuC}{\mathrm{l}}_3$ and the microscopic mechanisms underlying the emergence of spin liquid behavior.

Quantum coherence, encoded in the off-diagonal elements of a system's density matrix, is a key resource in quantum thermodynamics, fundamentally limiting the maximum extractable work known as ergotropy. While previous experiments have isolated coherence-related contributions to work extraction, it remains unclear how coherence can be harnessed in a controllable and energy-efficient manner. Here, we experimentally investigate the role of initial-state coherence in work extraction from a superconducting transmon qubit. By preparing a variety of pure states and implementing three complementary extraction protocols, we reveal how coherence governs the partitioning of ergotropy. We find that the choice of initial state depends on the dominant decoherence channel-energy relaxation or dephasing. By further accounting for thermodynamic costs, we identify optimal initial states that maximize the efficiency. Our results demonstrate that the initial-state design provides a scalable approach to coherence control and advances the development of efficient quantum thermodynamic devices.

We report radiation pressure slowing of YbF molecules to low velocity. In YbF, laser slowing is hindered by leaks out of the optical cycle attributed to low-lying metastable electronic states arising from inner-shell excitation. We bring this population back into the optical cycle once it has decayed to the electronic ground state using microwaves to couple the relevant rotational levels. We measure the scattering rate and closure of the optical cycle as repumps are added, and study the destabilization of dark states by a magnetic field and by polarization modulation, finding that both are helpful for maximizing the scattering rate. Starting from a beam with a mean speed of 80 m/s, and using frequency-broadened slowing light, we reduce the mean speed of the beam and produce a substantial flux in the low-velocity tail of the distribution. Slowing increases the fraction of molecules below 40 m/s from 0.4(1)% to 7.0(2)%, and the fraction below 30 m/s from zero to 3.2(1)%. The establishment of a nearly closed optical cycle and the production of molecules at low velocity are important steps toward trapping YbF molecules for future measurements of the electron's electric dipole moment.

The nontrivial integration of qubits with classical computing systems and the lack of quantum-memory devices remain a key obstacle in the development of quantum technologies. Here, we present a theoretical platform for hybrid quantum devices with memory characteristics. In these current-driven hybrid memristors, a ferroelectric layer serves as the tunneling barrier in a superconducting Josephson junction; thus, the potential barrier is history-dependent. A memory-integrated phase qubit and a Lagrangian description of the superconducting circuit are also presented, paving the way to highly functional, self-modulated Josephson-junction technologies.

We introduce Liouville-Fock-state lattices (LFSLs) as a framework for visualizing open quantum systems through matrix representations of the Lindblad master equation. These generalize Hamiltonian Fock-state lattices, which have been considered for realizing synthetic dimensions in quantum simulators. By vectorizing the Lindblad master equation, the dynamics map to a doubled Hilbert space, naturally forming a synthetic lattice. Unlike the unitary evolution of pure states, LFSLs feature non-Hermitian dynamics with drifts, sources, and sinks—paralleling stochastic classical lattices. As such, we suggest that these systems can serve as potential quantum simulators of classical lattice models, with a computational advantage arising from large state spaces encoded in quantum models. For this purpose, we analyze both the Fock representation and alternative positive-semidefinite representations that yield real, non-negative populations, akin to classical probability distributions. Within this formalism, we also demonstrate a phenomenon, which we term environment-induced frustration, in which competing terms in the LFSL give rise to geometric frustration and a massively degenerate steady-state manifold.

Optical solitons are self-sustained wave packets that propagate without distortion due to a balance between dispersion and nonlinearity. Their unique stability underpins key photonic applications while also playing a central role in nonlinear wave physics. However, real-time control over soliton dynamics in nondissipative systems remains a major challenge, limiting their practical applications in photonic systems. Here, we introduce a fiber-based platform for soliton manipulation, by creating programmable external potentials through synchronous arbitrary phase modulation in a recirculating optical fiber loop. We demonstrate precise soliton trapping, parametric excitation, and coupled multisoliton interactions, revealing particle-like behavior in excellent agreement with a Hamiltonian description in which solitons are treated as interacting particles. The strong analogy with matter-wave solitons in Bose-Einstein condensates highlights the broader implications of our approach, which provides a versatile experimental tool for the study of nonlinear wave dynamics and engineered soliton manipulation.

Non-Hermitian topology has revolutionized our understanding of energy gaps and band topology, unveiling phases that do not exist within the Hermitian framework. Nonetheless, its fundamental implications for quantum interactions in open quantum systems remain largely unexplored. Here, we uncover an interaction mechanism by examining a quantum-optical system where quantum emitters interact through the photonic band gap of a dissipative photon bath with periodic boundaries, described by a nonreciprocal Su-Schrieffer-Heeger model. Although localized photons within the gap should inhibit interactions between emitters in certain regimes, we find that interactions emerge even over long distances, defying conventional expectations. These anomalous interactions are mediated by a “mirage bath”—a virtual bath that unfolds onto a distinct layer of the Riemann surface. This mirage bath generates emitter dynamics identical to those produced by the physical bath but possesses distinct band topology. Crucially, the interactions inherit the topology of the mirage bath, not the physical one. This bath duality is universal to any dissipative bath with point gaps, leading to a mechanism for interactions and correlations across the multilayered Riemann surface, unseen in traditional settings. We demonstrate that the topological mismatch between the dual baths arises necessarily from their equivalent observable dynamics. We further show how such dynamical equivalence enforces the unification of non-Hermitian topologies with different boundaries. Our findings open avenues in quantum optics, many-body quantum simulations, and offer fresh insights into non-Hermitian topology.

Quantum access to arbitrary classical data encoded in unitary black-box oracles underlies interesting data-intensive quantum algorithms, such as machine learning or electronic structure simulation. The feasibility of these applications depends crucially on gate-efficient implementations of these oracles, which are commonly some reversible versions of the boolean circuit for a classical lookup table. We present a general parametrized architecture for quantum circuits implementing a lookup table that encompasses all prior work in realizing a continuum of optimal trade-offs between qubits, non-Clifford gates, and error resilience, up to logarithmic factors. Our architecture assumes only local 2D connectivity, yet recovers results, with the appropriate parameters, polylogarithmic error scaling. We also identify regimes, such as simultaneous sublinear scaling, in all parameters. These results enable tailoring implementations of the commonly used lookup table primitive to any given quantum device with constrained resources.

Phase separation routinely occurs in both living and synthetic systems. These phases are often complex and distinguished by features including crystallinity, nematic order, and a host of other nonconserved order parameters. For systems at equilibrium, the phase boundaries that characterize these transitions can be straightforwardly determined through the framework of thermodynamics. The prevalence of phase separation in active and driven systems motivates the need for a genuinely nonequilibrium theory for the coexistence of complex phases. Here, we develop a dynamical theory of coexistence when both conserved and nonconserved order parameters are present, casting coexistence criteria into the familiar form of equality of state functions. Our theory generalizes thermodynamic notions such as the chemical potential and Gibbs-Duhem relation to systems out of equilibrium. While these notions may not exist for all nonequilibrium systems, we numerically verify their existence for a variety of systems by introducing phenomenological active field theories. We hope our work aids in the development of a comprehensive theory of high-dimensional nonequilibrium phase diagrams.

The early prediction of tipping points, distinguished by sudden and catastrophic shifts from stable states, poses a challenging task that would enable us to assess the impending threat across natural and engineered systems. This threat becomes particularly acute in low-fluctuation environments, where tipping occurs through saddle-node bifurcation without prior warning in noise dynamics. In this study, we investigate the tipping point dynamics of avalanche catastrophes in low-fluctuation domain, employing model system like the zero-temperature random-field Ising model and thermally deposited cobalt films. As the system approaches the tipping point, avalanche activity reveals pronounced critical behavior, including critical slowing-down, variance enhancement, and a growing spatial correlation length—hallmarks that may serve as early warning signals of impending collapse. Crucially, we demonstrate that increasing disorder in the system reduces its vulnerability to catastrophic failure. In highly disorder regimes, these early warning signals emerge well before the transition, thereby providing a large margin for anticipation and mitigation. This key finding suggests a protective role of disorder offering a perspective on resilience in complex systems. Our results not only deepen the understanding of tipping phenomena in disorder materials but also have broader implications for forecasting regime shift in diverse real-world systems.

In this paper, we study the effects of plasmonic resonances on the Fisher information in the far field, of the position of a silver nanowire with respect to the center of a focused spot. We study theoretically a nanowire embedded in a high refractive index substrate that is illuminated by a dark-field focused spot. The position of the nanowire is determined from the scattered far-field intensities. The Fisher information is computed for both a lateral and longitudinal displacement of the nanowire, and its dependence on the illumination frequency is analyzed. The resonance frequencies of the nanowires are determined. We find that frequencies near a plasmonic resonance can enhance the Fisher information. However, at the resonance frequency itself and very close to it, the scattered far field corresponds to an information dark state. The phenomenon is demonstrated for silver, and the underlying physical mechanism is explained with an analytical model. As is shown, the dark state can be converted into a state with very high Fisher information about the positions of the nanowire by modifying the focused spot.

We propose and demonstrate a method to manipulate x-ray emission rates and directions by coupling them to surface plasmon polaritons via x-ray-to-ultraviolet down-conversion in a metal. This mechanism generates highly correlated photon pairs, each consisting of one x-ray and one ultraviolet photon, enabling fine control of x-ray angular and spectral characteristics through the ultraviolet photons resonant with the surface plasmons. Our approach bridges a previously insurmountable gap between x-ray and plasmonic energy and momentum, enabling the use of engineered plasmonic structures to control x-ray emission. Furthermore, our work unlocks opportunities to explore plasmonic physics at the microscopic scale with atomic-scale resolution.

The local magnetic anisotropy of a typical crystalline compound is usually attributed to the combined effect of crystal electric fields and spin-orbit coupling. We show that this simple local picture is transformed in heavy-fermion compounds by the development of coherent electron scattering from local spin degrees of freedom. Provided the dominance of the coherence energy scale over the magnetic energy scale is strong enough, the fractionalization and delocalization of the spins destabilizes their single-ion anisotropy by generating an opposing anisotropy in the exchange. Experimentally, this can manifest as competing splittings in the Curie-Weiss constants and effective moments. We show that in the presence of orthorhombic or tetragonal symmetry, the destabilization of the anisotropy can result in either ferromagnetic or antiferromagnetic order that is perpendicular to the high-temperature easy axis. In the absence of destabilization, we show that the order is more likely to be antiferromagnetic. In agreement with our theory, we also observe that the temperature at which the anisotropy of the uniform magnetic response changes tracks the coherence energy scale in a wide range of actinide and lanthanide compounds.

It has been demonstrated experimentally that friction forces between a two-dimensional (2D) material and an amorphous substrate are sufficient to stabilize tensile and compressive strains on the order of 1% within the 2D material. Here, a simple atomic-scale model is used to explore the friction between a 2D material and an idealized substrate. The atomic-scale model shows that the observed strains can be sustained by bonds with strengths on the order of van der Waals bonds. The model also reveals interesting atomic-scale structures at the interface that include vortices, antivortices, and other more complicated structures.

Distinguishing quantum states with minimal sampling overhead is of fundamental importance to teach quantum data to an algorithm. Recently, the quantum Wasserstein distance emerged from the theory of quantum optimal transport as a promising tool in this context. Here, we show on general grounds that the quantum Wasserstein distance between two ground states of a quantum critical system exhibits critical scaling. We demonstrate this explicitly using known closed analytical expressions for the magnetic correlations in the transverse field Ising model, to numerically extract the critical exponents for the distance close to the quantum critical point, confirming our analytical derivation. Our results have implications for learning of ground states of quantum critical phases of matter.

The modern theory of rare events is grounded in near-equilibrium ideas, however, many systems of modern interest are sufficiently far from equilibrium that traditional approaches do not apply. Using the recently developed variational path sampling methodology, we study systems evolving within nonequilibrium steady states to elucidate how reactive processes are altered away from equilibrium. Variational path sampling provides access to ensembles of reactive events and a means of quantifying the relative importance of each dynamical degree of freedom in such processes. With it, we have studied the conformational change of a solute in an active bath. We illustrate how energy injection generically enhances the rates of rare events, even when energy is not directed into specific reactive modes. By studying the folding and unfolding transitions of a grafted polymer under shear, we illustrate how nonequilibrium reactive processes do not follow gradient paths due to the emergence of persistent currents. The breaking of detailed balance allows for the mechanisms of forward and backward reactions to be distinct, enabling unconventional pathways to be explored and designed, and states unstable in equilibrium to become stabilized kinetically away from it. The analysis presented in this work establishes some basic principles for understanding the mechanism through which rates are perturbed by nonconservative forces, and how probability currents can stabilize thermodynamically unfavorable states, and is made possible by the use of a numerical method that does not invoke proximity to equilibrium.