$2H\text{−}{\mathrm{NbS}}_2$ is a classic example of an anisotropic multiband superconductor, with significant recent work focusing on the interesting responses seen when high magnetic fields are applied precisely parallel to the hexagonal niobium planes. It is often contrasted with its sister compound $2H\text{−}{\mathrm{NbSe}}_2$ because they have similar onset temperatures for superconductivity, but $2H\text{−}{\mathrm{NbS}}_2$ has no charge density wave whereas in $2H\text{−}{\mathrm{NbSe}}_2$ the charge density wave order couples strongly to the superconductivity. Using small-angle neutron scattering, a bulk-sensitive probe, we have studied the vortex lattice and how it responds to the underlying superconducting anisotropy. This is done by controlling the orientation of the field with respect to the Nb planes. The superconducting anisotropy, ${\mathrm{\Gamma }}_{ac}=7.07\pm 0.2$, is found to be field independent over the range measured (0.15 to 1.25 T), and the magnetic field distribution as a function of the applied magnetic field is found to be in excellent quantitative agreement with anisotropic London theory modified with a core-size cutoff correction, providing the first complete validation of this model. We find values of ${\lambda }_{ab}=141.9\pm 1.5$ nm for the in-plane London penetration depth, and ${\lambda }_c\sim 1\mu \mathrm{m}$ for the out-of-plane response. The field-independence indicates that we are primarily sampling the larger of the two gaps generating the superconductivity in this material.

Characterization of noise in current near-term quantum devices is of paramount importance to fully use their computational power. However, direct quantum process tomography becomes unfeasible for systems composed of tens of qubits. A promising alternative method based on tensor networks was recently proposed [Nat. Commun. 14, 2858 (2023)]. In this paper, we adapt it for the characterization of noise channels on near-term quantum computers and investigate its performance thoroughly. In particular, we show how experimentally feasible tomographic samples are sufficient to accurately characterize realistic correlated noise models affecting individual layers of quantum circuits, and study its performance on systems composed of up to 20 qubits. Furthermore, we combine this noise characterization method with a recently proposed noise-aware tensor network error mitigation protocol for correcting outcomes in noisy circuits, resulting accurate estimations even on deep circuit instances. This positions the tensor-network-based noise characterization protocol as a valuable tool for practical error characterization and mitigation in the near-term quantum computing era.

Probabilistic context-free grammars (PCFGs), which are commonly used to generate trees randomly, have been well analyzed theoretically, leading to applications in various domains. Despite their utility, the distributions that the grammar can express are limited to those in which the distribution of a subtree depends only on its root and not on its context. This limitation presents a challenge for modeling various real-world phenomena, such as natural languages. To overcome this limitation, a probabilistic context-sensitive grammar (PCSG) is introduced, where the distribution of a subtree depends on its context. Numerical analysis of a PCSG reveals that the distribution of a symbol does not constitute a qualitative difference from that in the context-free case, but mutual information does. Furthermore, a novel metric introduced to directly quantify the breaking of this limitation detects a distinct difference between PCFGs and PCSGs. This metric, applicable to an arbitrary distribution of a tree, allows for further investigation and characterization of various tree structures that PCFGs cannot express.

While the accuracy of qubit operations has been greatly improved in the last decade, further development is demanded to achieve the ultimate goal: a fault-tolerant quantum computer that can solve real-world problems more efficiently than classical computers. With growing fidelities even subtle effects of environmental noise such as qubit–reservoir correlations and non-Markovian dynamics turn into the focus for both circuit design and control. To guide progress, we disclose, in a numerically rigorous manner, a comprehensive picture of the single-qubit dynamics in presence of a broad class of noise sources and for entire sequences of gate operations. Thermal reservoirs ranging from Ohmic to deep $1/f^{\varepsilon }$-like sub-Ohmic behavior are considered to imitate realistic scenarios for superconducting qubits. Apart from dynamical features, fidelities of the qubit performance over entire sequences are analyzed as a figure of merit. The relevance of retarded feedback and long-range qubit–reservoir correlations is demonstrated on a quantitative level, thus, providing a deeper understanding of the limitations of performances for current devices and guiding the design of future ones.

Bacteria employ diverse swimming patterns for chemotaxis, influenced by factors including flagellar arrangements, motor rotation, flagellar filament configurations, and polymorphism. Understanding the chemotactic strategy of Aliivibrio fischeri in locating a squid partner is paramount for comprehending this highly species-specific symbiosis. In this study, we applied three-dimensional swimming tracking and real-time visualization of lophotrichous flagellar configurations. These techniques unveiled viscosity-dependent transitions in swimming patterns, shifting from push-pull to push-wrap modes. Notably, our research also revealed coupled flagellar switching and polymorphic transformations during the wrap mode, significantly extending A. fischeri's backward swimming duration and, consequently, its overall runtime. This strategic adaptation allows A. fischeri to broaden its effective search range, particularly within high-viscosity environments like the squid light organ. In response to attractants, the coupling rate is reduced to facilitate efficient short-range searching. These innovative chemotactic strategies ensure precise navigation for A. fischeri in locating and colonizing its symbiotic partner, the squid Euprymna scolopes.

The energy landscape of sodium chloride-nitrogen mixtures has been comprehensively explored to examine the ability of the formation of unknown compounds under pressures of up to 100 GPa, using swarm-intelligence structure prediction methodology and first-principles calculations. We identified a thermodynamically stable ${\mathrm{NaN}}_5{\mathrm{ClN}}_5$ compound containing two cyclo-${\mathrm{N}}_5$ species under pressures exceeding 53 GPa, representing milder conditions in comparison to those requisite for pure solid nitrogen. In ${\mathrm{NaN}}_5{\mathrm{ClN}}_5$, the high electron affinity of the cyclo-${\mathrm{N}}_5$ motif allows it to oxidize the chlorine atoms, resulting in the formation of two cyclo-${\mathrm{N}}_5$ anions. Additionally, the weak covalent interactions between Cl and nearby N atoms plays a key role in stabilization of structure. It has been demonstrated that simple ${\mathrm{NaN}}_5$ salt was a suitable precursor for the synthesis of ${\mathrm{NaN}}_5{\mathrm{ClN}}_5$ at high pressure. Ab initio molecular dynamics simulations demonstrated the recoverability of ${\mathrm{NaN}}_5{\mathrm{ClN}}_5$ as a metastable phase at ambient pressure-temperature conditions. Additionally, ${\mathrm{NaN}}_5{\mathrm{ClN}}_5$ exhibits a higher energy density of 3.86 kJ/g and a lower mass density of 1.67 g/${\mathrm{cm}}^3$ in comparison to metal pentazolate salts, highlighting its potential as a high energy-density material.

Establishing limits of entanglement in open quantum systems is a problem of fundamental interest, with strong implications for applications in quantum information science. Here, we study the limits of entanglement stabilization between remote qubits. We theoretically investigate the loss resilience of driven-dissipative entanglement between remote qubits coupled to a chiral waveguide. We find that by coupling a pair of storage qubits to the two driven qubits, the steady state can be tailored such that the storage qubits show a degree of entanglement that is higher than what can be achieved with only two driven qubits coupled to the waveguide. By reducing the degree of entanglement of the driven qubits, we show that the entanglement between the storage qubits becomes more resilient to waveguide loss. Our analytical and numerical results offer insights into how waveguide loss limits the degree of entanglement in this driven-dissipative system, and they offer important guidance for remote entanglement stabilization in the laboratory, for example using superconducting circuits.

Langevin dynamics simulations of two-dimensional (2D) Yukawa solids are performed to investigate the orientation-dependent yield and Bauschinger effects in solid 2D dusty plasmas. The yield stress of 2D Yukawa solids under different conditions is determined from the corresponding stress-strain response curve, defect fraction, and deviation from the affine displacement. It is discovered that both the shear modulus and yield stress are orientation dependent, exhibiting the significant anisotropic behaviors. It is found that the dependence of the calculated atomic elastic constant on the lattice orientation completely agrees with those of the shear modulus and yield stress. It is also found that, for different initial lattice orientations, the Yukawa solid exhibits the significant regular or reverse Bauschinger effects, or even non-Bauschinger effect.

Liquid droplets on soft solids, such as soft polymeric gels, can induce substantial surface deformations, leading to the formation of wetting ridges at contact points. While these contact ridges have been shown to govern the rich surface mechanics on compliant substrates, the inherently divergent characteristics of contact points and the multiphase nature of soft reticulated gels pose great challenges for continuum mechanical theories in modeling soft wetting phenomena. In this study, we report in situ experimental characterizations of the emergence and growth dynamics of the wetting-induced phase separation. The measurements demonstrate how the migration of free chains prevents the stress singularities at contact points. Based on the Onsager variational principle, we present a phenomenological model that effectively captures the extraction process of free chains, including a crossover from a short-term diffusive state to a long-term equilibrium state. By comparing model predictions with experimental results for varied crosslinking densities, we reveal how the intrinsic material parameters of soft gels dictate phase-separation dynamics.

Cell monolayers and epithelial tissues display slow relaxation dynamics during the reversible transition between mesenchymal and epithelial cells, a phenomenon directly relevant to embryogenesis, tumor metastases, and wound healing. In active cells, persistent motion induces collective dynamics that significantly influence relaxation behavior. To better understand the role of persistence in cell relaxations, we perform extensive simulations and employ cage-relative measures to address the previously overlooked system size effects in model active cells. We identify the glass transition at various persistence values, demonstrating conventional near-equilibrium supercooled dynamics at low persistence. However, highly persistent cells exhibit distinctive intermittent dynamics associated with intermittent local T1 transitions, where cell velocity correlates over space with a characteristic length $\xi$. More significantly, we formulate a universal relationship predicting the global relaxation time based on the T1 transition and the spatial velocity correlation across a wide range of persistence values. Specifically, the relaxation time demonstrates a power-law dependence on the irreversible T1 transition rate, multiplied by $\exp \left(\xi \right)$. Here, $\xi$ vanishes at small persistence in nearly equilibrated cells, and the irreversible T1 transition rate diminishes towards the mode-coupling glass transition point.

Most biomolecular systems exhibit computation abilities, which are often achieved through complex networks such as signal transduction networks. Particularly, molecular competition in these networks can introduce crosstalk and serve as a hidden layer for cellular information processing. Despite the increasing evidence of competition contributing to efficient cellular computation, how this occurs and the extent of computational capacity it confers remain elusive. In this study, we introduced a mathematical model for molecular competition networks (MCNs) and employed a machine learning-based optimization method to explore their computational capacity. Our findings revealed that MCNs, when compared to their noncompetitive counterparts, demonstrate superior performance in both discrete decision-making and analog computation tasks. Furthermore, we highlighted the nonnegligible role of weak interactions and limited amounts of resources and examined how biological constraints influence the computational capacity of MCNs. The study suggested the potential of MCNs as efficient computational structures and provided new insights into cellular information processing.

There has been a growing interest in non-Hermitian physics. One of its main goals is to engineer dissipation and to explore ensuing functionality. In magnonics, the effect of dissipation due to local damping on magnon transport has been explored. However, the effects of nonlocal damping on the magnonic analog of the Josephson effect remain missing, despite that nonlocal damping is inevitable and has been playing a central role in magnonics. Here, we uncover theoretically that a surprisingly rich dynamics can emerge in magnetic junctions due to intrinsic nonlocal damping, using analytical and numerical methods. In particular, under microwave pumping, we show that coherent spin precession in the right and left insulating ferromagnet (FM) of the junction becomes synchronized by nonlocal damping and thereby a magnonic analog of the $\phi$ Josephson junction emerges, where $\phi$ stands here for the relative precession phase of right and left FM in the stationary limit. Remarkably, $\phi$ decreases monotonically from $\pi$ to $\pi /2$ as the magnon-magnon interaction, arising from spin anisotropies, increases. Moreover, we also find a magnonic diode effect giving rise to rectification of magnon currents. Our predictions are readily testable with current device and measurement technologies at room temperatures.

The Kitaev interaction, found in candidate materials such as $\alpha \text{−}{\mathrm{RuCl}}_3$, occurs through the metal ($M$)-ligand ($X$)-metal ($M$) paths of the edge-sharing octahedra because the large spin-orbit coupling (SOC) on the metal atoms activates directional spin interactions. Here, we show that even in $3d$ transition-metal compounds, where the SOC of the metal atom is negligible, heavy ligands can induce bond-dependent Kitaev interactions. In this work, we take as an example the $3d$ transition-metal chalcogenophosphate ${\mathrm{NiPSe}}_3$ and show that the key is found in the presence of a sizable SOC on the Se $p$ orbital, one which mediates the super-exchange between the nearest-neighbor Ni sites. Our study provides a pathway for engineering enhanced Kitaev interactions through the interplay of SOC strength, lattice distortions, and chemical substitutions.

Topology is routinely used to understand the physics of electronic insulators. However, for strongly interacting electronic matter, such as Mott insulators, a comprehensive topological characterization is still lacking. When their ground state only contains short-range entanglement and does not break symmetries spontaneously, they generically realize crystalline fermionic symmetry-protected topological phases (cFSPTs), supporting gapless modes at the boundaries or at the lattice defects. Here, we provide an exhaustive classification of cFSPTs in two dimensions with $\mathrm{U}\left(1\right)$ charge-conservation and spinful time-reversal symmetries, namely, those generically present in spin-orbit coupled insulators, for any of the 17 wallpaper groups. It has been shown that the classification of cFSPTs can be understood from appropriate real-space decorations of lower-dimensional subspaces, and we expose how these relate to the Wyckoff positions of the lattice. We find that all nontrivial one-dimensional decorations require electronic interactions. Furthermore, we provide model Hamiltonians for various decorations, and discuss the signatures of cFSPTs. This classification paves the way to further explore topological interacting insulators, providing the backbone information in generic model systems and ultimately in experiments.

Transmission lines (TLs) are excellent examples of quantum simulators of quantum fields. By appropriately driving-specific circuit elements, these devices can reproduce relativistic and quantum phenomena such as particle creation due to the nonadiabatic stimulation of the quantum vacuum. We investigate particle creation in left-handed TLs induced by the modulation of the Josephson energy in superconducting quantum interference devices. Our results show that, as a consequence of the peculiar dispersion relations present in these systems, particle production occurs with much more favorable conditions with respect to the usual right-handed TLs.

What are the fundamental limits and advantages of using a catalyst to aid thermodynamic transformations between quantum systems? In this paper, we answer this question by focusing on transformations between energy-incoherent states under the most general energy-conserving interactions among the system, the catalyst, and a thermal environment. The sole constraint is that the catalyst must return unperturbed and uncorrelated with the other subsystems. More precisely, we first upper bound the set of states to which a given initial state can thermodynamically evolve (the catalyzable future) or from which it can evolve (the catalyzable past) with the help of a strict catalyst. Secondly, we derive lower bounds on the dimensionality required for the existence of catalysts under thermal process, along with bounds on the catalyst's state preparation. Finally, we quantify the catalytic advantage in terms of the volume of the catalyzable future and demonstrate its utility in an exemplary task of generating entanglement and cooling a quantum system using thermal resources.