The spontaneous formation of contractile asters is ubiquitous in reconstituted active materials composed of biopolymers and molecular motors. Asters are radially oriented biopolymers or biopolymer bundles with a dense motor-rich core. The microscopic origins of their material properties and their stability are unknown. Recent efforts highlighted how motor-filament and filament-filament interactions control the formation of asters composed of microtubules and kinesin motors. However, the impact of motor-motor interactions is less understood, despite growing evidence that molecular motors often spontaneously aggregate, both in vitro and in vivo. In this article, we combine experiments and simulations to reveal the origin of the arrested coarsening, aging, and stability of contractile asters composed of microtubules, clusters of adenosine triphosphate (ATP)-powered kinesin-1 motors, and a depletant. Asters coalesce into larger asters upon collision. We show that the spontaneous aggregation of motor clusters drives the solidification of aster cores, arresting their coalescence. We detect aggregation of motor clusters at the single microtubule level, where the uncaging of additional ATP drives the delayed but sudden detachment of large motor aggregates from isolated microtubules. Computer simulations of cytoskeletal assemblies demonstrate that decreasing the motors' unbinding rate slows down the aster's coalescence. Changing the motors' binding rate did not impact the aster's coalescence dynamics. Finally, we show that the aggregation of motor clusters and aster aging result from the combined effects of depletion forces and nonspecific binding of the clusters to themselves. We propose alternative formulations that mitigate these effects, and prevent aster aging. The resulting self-organized structures have a finite lifetime, which reveals that motor aggregation is crucial for maintaining aster's stability. Overall, these experiments and simulations enhance our understanding of how to rationally design long-lived and stable contractile materials from cytoskeletal proteins.

In this paper, we propose a paradigm for atom interferometry and demonstrate that there exists a universal set of atom optic components for inertial sensing. These components constitute gates with which we carry out quantum operations and represent input-output matter wave transformations between lattice eigenstates. Each gate is associated with a modulation pattern of the position of the optical lattice according to machine-designed protocols. In this methodology, a sensor can be reprogramed to respond to an evolving set of design priorities without modifying the hardware. We assert that such a gate set is metrologically universal, in analogy to universal gate sets for quantum computing. Experimental confirmation of the designed operation is demonstrated via in situ imaging of the spatial evolution of a Bose-Einstein condensate in an optical lattice and by measurement of the momentum probabilities following time-of-flight expansion. The representation of several basic quantum sensing circuits is presented for the measurement of inertial forces, rotating reference frames, and gravity gradients.

Thermodynamic force and irreversible current are the foundational concepts of classical nonequilibrium thermodynamics. Entropy production rate is provided by their product in classical systems, ranging from mesoscopic to macroscopic systems. However, there is no complete quantum extension of such a structure that respects quantum mechanics. In this paper, we propose anti-Hermitian operators that represent currents and forces accompanied by a gradient structure in open quantum systems described by the quantum master equation. We prove that the entropy production rate is given by the product of the force and current operators, which extends the canonical expression of the entropy production rate in the classical systems. The framework constitutes a comprehensive analogy with the nonequilibrium thermodynamics of discrete classical systems. We also show that the structure leads to the extensions of some results in stochastic thermodynamics: the geometric housekeeping-excess decomposition of entropy production and thermodynamic trade-off relations such as the thermodynamic uncertainty relation and the dissipation-time uncertainty relation. In discussing the trade-off relations, we will introduce a measure of fluctuation, which we term the quantum diffusivity.

XY mixer are a type of mixing Hamiltonians used in the quantum alternating operator ansatzs (QAOA) framework for solving combinatorial optimization problems where the feasible subspace consists of states with the same Hamming weight. In this paper, we propose an extension of the XY-mixer ansatzes to solve optimization problems that do not adhere to this specific subspace structure. For problems, such as maximal independent set, one can employ positive semidefinite programming and a greedy algorithm to obtain upper and lower bounds for the optimal solution, then utilize the XY-mixer ansatzes in the separated subspaces between the upper and lower bounds to address the problem at hand. Additionally, we find suitable counterdiabatic (CD) driving terms that complement the XY-mixer ansatzes. These driving terms accelerate the QAOA evolution towards the target state and also confine the evolution within the subspace. By combining XY-mixer ansatzes with counterdiabatic driving (XY-CD mixers), we present a generalized QAOA-based scheme for finding higher-quality approximate solutions to combinatorial problems.

Despite recent numerical evidence, one of the fundamental theoretical mysteries of polaritonic chemistry is how and if collective strong coupling can induce local changes of the electronic structure to modify chemical properties. Here we present nonperturbative analytic results for a model system consisting of an ensemble of $N$ harmonic molecules under vibrational strong coupling (VSC) that alters our present understanding of this fundamental question. By applying the cavity Born-Oppenheimer partitioning on the Pauli-Fierz Hamiltonian in dipole approximation, the dressed many-molecule problem can be solved nonperturbatively and analytically in the dilute limit, i.e., a self-consistent solution with the mean-field Hartree-product wave function becomes exact. We discover that the electronic molecular polarizabilities are modified even in the case of vanishingly small single-molecule couplings. Consequently, this nonperturbative local polarization mechanism persists even in the large-$N$ limit. In contrast, a perturbative calculation of the polarizabilities based on the uncoupled ensemble wave function leads to a qualitatively erroneous scaling behavior with vanishing effects in the large-$N$ limit. Nevertheless, the exact (self-consistent) polarizabilities can be determined from single-molecule strong coupling simulations instead. Our fundamental theoretical observations demonstrate that hitherto existing collective-scaling arguments are insufficient for polaritonic chemistry and they pave the way for refined single- (or few-)molecule strong-coupling ab initio simulations of chemical systems under collective strong coupling.

In the study of nonlinear dynamics and chaos, analytically solvable physical models are rare. We investigate the classical motion of a trapped relativistic particle, subject to an electric and a magnetic field. When the directions of the electric and magnetic fields coincide, the dynamics are integrable. As the magnetic field rotates away from the direction of the electric field, a transition to chaos occurs. Based on the approach in a previous work in the nonrelativistic regime [Narimanov et al., Phys. Rev. B 57, 9807 (1998)], we introduce a particular Lorentz transformation to extend the framework to the relativistic regime, which enables us to derive the Poincaré map and obtain semianalytic formulas for periodic orbits of low periods. The transformation also makes it possible to assess, semianalytically, the role of the degree of the relativistic motion of the particle in its dynamics, revealing that the special relativity effects can enhance chaos. As numerical simulations have played a dominant role in investigating nonlinear physical systems exhibiting chaos and in many cases are the only feasible tool to probe into the system dynamics, our semianalytic approach is unique and leads to additional insights into the interplay between special relativity and chaos.

Intense laser plasma driven ion acceleration is typically based on a target normal sheath acceleration scheme. This demands short density scale length plasmas and relativistic intensity laser pulses. Parametric instabilities driving electron acceleration in long density scale length plasmas have seldom been considered in this context. We provide the first experimental evidence for ion acceleration driven by parametric two plasmon decay (TPD) instability. In this regime, laser pulses with intensities hundredfold below relativistic thresholds are enough to produce MeV energy hot electrons. This allows mJ energy laser pulses to drive ion beams up to 0.6 MeV energy with ${20}^{\circ }$ angular width. Ion source size $<15$ $\mu \text{m}$ are observed via ion radiography, steady over thousands of shots.

We propose an innovative method to enhance the detection and protection of quantum entanglement, a cornerstone of quantum mechanics with applications in computing, communication, and beyond. While entanglement can be represented through nonlocal correlations detectable by the Clauser-Horne-Shimony-Holt (CHSH) inequality, this method does not fully capture all entangled states. To address this limitation, we introduce a variational entanglement witness (VEW) that optimizes the probabilities of detection and improves the efficiency of distinguishing between separable and entangled states. Additionally, we propose a nonlocal measurement framework that enables the assessment of both CHSH inequalities and the VEW while preserving the entanglement. Our approach enhances the reliability of entanglement detection while maintaining the entanglement of quantum states, offering significant advancements for quantum technologies.

Multiquanta emission holds significant value for quantum computing and quantum information processing. In this study, we aim to enhance multiphoton bundle emission by introducing two-photon decay into cavity quantum electrodynamics systems. By implementing parity protection induced by two-photon decay in the quantum jump process, we achieve complete suppression of odd photon emissions, resulting in high-purity, high-efficiency $2n$-photon bundle emission characterized by photon bunching and bundle antibunching. Our results indicate that this scheme can effectively produce $2n$-photon sources. Unlike previous methods that enhanced $2n$-photon bundle purity via parity protection during unitary processes which required ultrastrong cavity-atom coupling, this study is the first to focus on parity protection during nonunitary processes to improve emission purity. This innovative approach not only relaxes the ultrastrong coupling condition compared to earlier schemes, but it also opens new research directions for enhancing $N$-photon bundle emission. Furthermore, this work has the potential to advance the fields of multiphoton physics and parity theory.

Gradient-based optimization methods are the established state-of-the-art paradigm to study strongly entangled quantum systems in two dimensions with projected entangled pair states. However, the key ingredient, the gradient itself, has proven challenging to calculate accurately and reliably in the case of a corner transfer matrix-based approach. Automatic differentiation (AD), which is the best known tool for calculating the gradient, still suffers some crucial shortcomings. Some of these are known, like the problem of excessive memory usage and the divergences which may arise when differentiating a singular value decomposition (SVD). Importantly, we find that there is also a fundamental inaccuracy in the currently used backpropagation of SVD that had not been noted before. In this paper, we describe all these problems and provide them with compact and easy to implement solutions. We analyze the impact of these changes and find that the last problem—the use of the correct gradient—is by far the dominant one and thus should be considered a crucial patch to any AD application that makes use of an SVD for truncation.

Human movement in an urban environment consists of a complex system where the results and observations of an analysis may be dependent on the choice of resolutions. In this study, a two-dimensional lattice weighted undirected graph embedded in Euclidean space is constructed to represent human flow in an urban environment. Specifically, each node represents an area whereas a link consists of a road connecting two adjacent areas. People moving in a grid under a specific resolution are aggregated, and the sum of their velocity is assigned as the link weight. Based on the analysis of real-world GPS data, we first find that the human potential in the revised electric circuit model (RECM) can characterize the spatial-temporal human movement trends in an urban environment independent of different observation resolutions. Second, we propose several renormalization methods for three analogical concepts in the RECM, namely, human current, human resistance, and human potential. Each of these can be used to describe spatial-temporal flow patterns, infrastructure level, and movement trends, respectively, to reveal their relation under different spatial resolutions. Third, we find a nontrivial scaling relation, which may be regarded as a new type of gravity relation, to characterize the heterogeneous spatial distribution of human conductivity. Although the power exponent of distance $\gamma$ in the above relation slightly changes at different spatial scales, a nontrivial relation is derived to explain and estimate the exponent automatically. Overall, these discoveries may lead to new approaches for establishing a cross-scale human mobility description framework.

Motility and nonreciprocity are two primary mechanisms for self-organization in active matter. In a recent study [Phys. Rev. Lett. 131, 148301 (2023)], we explored their joint influence in a minimal model of two-species quorum-sensing active particles interacting via mutual motility regulation. Our results notably revealed a highly dynamic phase of chaotic chasing bands that is absent when either nonreciprocity or self-propulsion is missing. Here, we examine further the phase behavior of nonreciprocal quorum-sensing active particles, distinguishing between the regimes of weak and strong nonreciprocity. In the weakly nonreciprocal regime, this system exhibits multicomponent motility-induced phase separation. We establish an analytical criterion for the associated phase coexistence, enabling a quantitative prediction of the phase diagram of a large class of nonreciprocal mixtures. For strong nonreciprocity, where the dynamics is chase-and-run-like, we determine the phase behavior and show that it depends strongly on the scale of observation. In small systems, our numerical simulations reveal a phenomenology consistent with phenomenological models, comprising traveling phase-separated domains and spiral-like defect patterns. However, we show that these structures are generically unstable in large systems, where they are superseded by bulk phase coexistence between domains that are either homogeneous or populated by mesoscopic chasing bands. Crucially, this implies that collective motion totally vanishes at large scales, while the breakdown of our analytical criterion for this phase coexistence with multiscale structures prevents us from predicting the corresponding phase diagram.

Magnetic refrigeration represents an environmentally friendly and promising technology for cooling applications, particularly in hydrogen liquefaction. Recent advancements have demonstrated a highly efficient cooling protocol utilizing small magnetic-field oscillations near metamagnetic transitions, tested using pure holmium metal. This study investigates ternary alloys substituted with erbium and cerium, specifically ${\mathrm{Ho}}_{100\text{−}x\text{−}y}{\mathrm{Er}}_x{\mathrm{Ce}}_y$ $(x<100,$ $y<21)$, to further enhance the performance of the refrigerant. The control of magnetic entropy is largely dependent on identifying variations in spin configurations. However, analyzing these variations in ternary alloys through neutron diffractometry is time intensive. To address this challenge, a multisample neutron transmission spectroscopy technique was developed and applied at beamline 22 RADEN at Japan Proton Accelerator Research Complex (J-PARC). This approach enabled the simultaneous observation of transmission spectra for 25 different alloy compositions at cryogenic temperatures. The spectra revealed that cerium-doped, erbium-rich alloys primarily exhibit ferromagnetic components, yielding a magnetocaloric effect that exceeds that of pure holmium metal under a 5-T magnetic field. In other alloy compositions, the presence of antiferromagnetic ordered states was indicated by satellite Bragg edges in the spectrum. The magnetocaloric effects associated with metamagnetic transitions from these states tend to diminish as the transitions become more frequent or diffuse due to the alloying. The insights gained from this spectroscopic technique contribute to our understanding of the variations in magnetocaloric properties as a result of alloying. Moreover, the successful simultaneous determination of spin configurations across numerous samples highlights the potential of this spectroscopic approach for widespread use in magnetic property evaluation, particularly in the realm of big data-driven research.

We present a method utilizing atomic diffraction patterns and statistical analysis tools to infer the Casimir-Polder interaction between argon atoms and a silicon nitride nanograting. The quantum model that supports the data is investigated in detail, as are the roles of nanograting geometry, finite-size effects, slit width opening angles, Lennard-Jones potentials, and patch potentials. Our findings indicate that the atom-surface potential strength parameter is $C_3=6.9\pm 1.2\mathrm{meV}{\mathrm{nm}}^3$. This value is primarily constrained by the knowledge of the nanograting geometry. The high sensitivity of our method paves the way for precise determination of the Casimir-Polder potential and exploration of new short-distance forces.