In ${\mathrm{Eu}}_2\mathrm{ZnIr}{\mathrm{O}}_6$, effectively two atoms are active; i.e., Ir is magnetically active, which results in complex magnetic ordering within the Ir sublattice at low temperature. On the other hand, although Eu is a Van Vleck paramagnet, it is active in the electronic channels involving $4f^6$ crystal-field split levels. Phonons, quanta of lattice vibration involving vibration of atoms in the unit cell, are intimately coupled with both magnetic and electronic degrees of freedom (DOF). Here, we report a comprehensive study focusing on the phonons as well as intraconfigurational excitations in double-perovskite ${\mathrm{Eu}}_2\mathrm{ZnIr}{\mathrm{O}}_6$. Our studies reveal strong coupling of phonons with the underlying magnetic DOF reflected in the renormalization of the phonon self-energy parameters well above the spin-solid phase ($T_N\sim 12\mathrm{K}$) until temperature as high as $\sim 3T_N$ evidences broken spin rotational symmetry deep into the paramagnetic phase. In particular, all the observed first-order phonon modes show softening of varying degree below $\sim 3T_N$, and low-frequency phonons become sharper, while the high-frequency phonons show broadening attributed to the additional available magnetic damping channels. We also observed a large number of high-energy modes, 39 in total, attributed to the electronic transitions between $4f$ levels of the rare-earth ${\mathrm{Eu}}^{3+}$ ion and these modes shows anomalous temperature evolution as well as mixing of the crystal-field split levels attributed to the strong coupling of electronic and lattice DOF.

We discuss the connection between the out-of-time-ordered correlator and the number of harmonics of the phase-space Wigner distribution function. In particular, we show that both quantities grow exponentially for chaotic dynamics, with a rate determined by the largest Lyapunov exponent of the underlying classical dynamics, and algebraically—linearly or quadratically—for integrable dynamics. It is then possible to use such quantities to detect in the time domain the integrability-to-chaos crossover in many-body quantum systems.

Indium-cluster anions ${\mathrm{In}}_n^{-}$ are probed for delayed dissociation by photoexcitation in a multi-reflection time-of-flight device. In addition to prompt dissociation with below-microsecond decay constants, we observe reactions on timescales of several tens to hundreds of microseconds. These time-resolved decay-rate measurements reveal a power-law behavior in time which can be traced back to the clusters' energy distribution due to their production by laser ablation in high vacuum. Modeling energy distributions from such a production allows us to connect the cluster-specific dissociation energy with the ensemble temperature through experimentally determined power-law exponents.

The electromagnetic scattering resonances and modes of a nonmagnetic object much smaller than the incident wavelength in vacuum can be either described by the electroquasistatic approximation of the Maxwell's equations if its permittivity is negative or by the magnetoquasistatic approximation if its permittivity is positive and sufficiently high. Nevertheless, these two approximations fail to correctly account for the frequency shift and the radiative broadening of the resonances when the size of the object becomes comparable to the wavelength of operation. In this paper, the radiation corrections to the electroquasistatic and magnetoquasistatic resonances and modes of arbitrarily shaped objects are derived, which only depend on the quasistatic current modes. Then, closed-form expressions of the frequency shift and the radiative Q-factor of both plasmonic and dielectric modes of small objects are introduced, where the dependencies on the material and the size of the object are factorized. In particular, it is shown that the radiative Q-factor explicitly depends on the multipolar components of the quasistatic mode and its corrections.

Single shot x-ray diffraction (XRD) experiments have been performed with an x-ray free electron laser under pulsed high magnetic fields up to 16 T generated with a nondestructive minicoil. The antiferromagnetic insulator phase in a perovskite manganaite, ${\mathrm{Pr}}_{0.6}{\mathrm{Ca}}_{0.4}{\mathrm{MnO}}_3$, is collapsed at a magnetic field of $\approx 8$ T with an emergence of the ferromagnetic metallic phase, which is observed via the accompanying lattice changes in a series of the single shot XRD. We discussed the feasibility of the single shot XRD experiment under ultrahigh magnetic fields beyond 100 T, which is generated with a portable destructive pulse magnet.

Many search processes are conducted in the vicinity of a favored location, i.e., a home, which is visited repeatedly. Foraging animals return to their dens and nests to rest, scouts return to their bases to resupply, and drones return to their docking stations to recharge or refuel. Yet, despite its prevalence, very little is known about search with home returns because its analysis is much more challenging than that of unconstrained, free-range search. Here, we develop a theoretical framework for search with home returns. This makes no assumptions on the underlying search process and is furthermore suited to treat generic return and home-stay strategies. We show that the solution to the home-return problem can then be given in terms of the solution to the corresponding free-range problem—which not only reduces overall complexity but also gives rise to a simple and universal phase-diagram for search. The latter reveals that search with home returns outperforms free-range search in conditions of high uncertainty. Thus, when living gets rough, a home will not only provide warmth and shelter but also allow one to locate food and other resources quickly and more efficiently than in its absence.

We demonstrate that an ultrashort high intensity laser pulse can propagate for hundreds of Rayleigh ranges in a prepared neutral hydrogen channel by generating its own plasma waveguide as it propagates; the front of the pulse generates a waveguide that confines the rest of the pulse. A wide range of suitable initial index structures and gas densities will support this “self-waveguiding” process; the necessary feature is that the gas density on axis is a minimum. Here, we demonstrate self-waveguiding of pulses of at least $1.5\times {10}^{17}\mathrm{W}/{\mathrm{cm}}^2$ (normalized vector potential $a_0\sim 0.3$) over 10 cm, or $\sim 100$ Rayleigh ranges, limited only by our laser energy and length of our gas jet. We predict and observe characteristic oscillations corresponding to mode-beating during self-waveguiding. The self-waveguiding pulse leaves in its wake a fully ionized low-density plasma waveguide which can guide another pulse injected immediately following; we demonstrate optical guiding of such a follow-on probe pulse. The method is well suited to laser wakefield acceleration and other applications requiring a long laser-matter interaction length.

All phase-encoded BB84 implementations have signal states with unbalanced amplitudes in practice. Thus the original security analyses a priori do not apply to them. Previous security proofs use signal tagging of multiphoton pulses to recover the behavior of regular BB84. This is overly conservative as for unbalanced signals the photon number splitting attack does not leak full information to Eve. In this work we exploit the flag-state squashing model to preserve some parts of the multiphoton-generated private information in our analysis. Using a numerical proof technique we obtain significantly higher key rates compared with previously published results in the low-loss regime. It turns out that the usual scenario of untrusted dark counts runs into conceptual difficulties in some parameter regimes. Thus we discuss the trusted dark-count scenario in this paper as well. We also report a gain in key rates when part of the total loss is known to be induced by a trusted device. We highlight that all these key rate improvements can be achieved without modification of the experimental setup.

Recent work on self-organized remodeling of vasculature in slime molds, leaf venation systems, and vessel systems in vertebrates has put forward a plethora of potential adaptation mechanisms. All these share the underlying hypothesis of a flow-driven machinery, meant to alter rudimentary vessel networks in order to optimize the system's dissipation, flow uniformity, or more, with different versions of constraints. Nevertheless, the influence of environmental factors on the long-term adaptation dynamics as well as the network structure and function have not been fully understood. Therefore, interwoven capillary systems such as those found in the liver, kidney, and pancreas present a novel challenge and key opportunity regarding the field of coupled distribution networks. We here present an advanced version of the discrete Hu-Cai model, coupling two spatial networks in three dimensions. We show that spatial coupling of two flow-adapting networks can control the onset of topological complexity in concert with short-term flow fluctuations. We find that both fluctuation-induced and spatial coupling induced topology transitions undergo curve collapse, obeying simple functional rescaling. Further, our approach results in an alternative form of Murray's law, which incorporates local vessel interactions and flow interactions. This geometric law allows for the estimation of the model parameters in ideal Kirchhoff networks and respective experimentally acquired network skeletons.

Thin garnet films with perpendicular anisotropy are enjoying renewed attention in the context of research on heavy metal/ferromagnetic insulator bilayer devices with tunable electric and magnetic properties. We show that two temperature-induced magnetic orientation transitions observed in such films have different origins. One transition occurs between the uniform, in-plane magnetized state and the stripe domain state, and is governed by the bulk material properties. The other occurs between the domain state and the perpendicular magnetized uniform state, and is governed by the physics of domain nucleation.

Evolutionary games provide the theoretical backbone for many aspects of our social life: from cooperation to crime, from climate inaction to imperfect vaccination and epidemic spreading, from antibiotics overuse to biodiversity preservation. An important, and so far overlooked, aspect of reality is the diverse strategic identities of individuals. While applying the same strategy to all interaction partners may be an acceptable assumption for simpler forms of life, this fails to account for the behavior of more complex living beings. For instance, we humans act differently around different people. Here we show that allowing individuals to adopt different strategies with different partners yields a very rich evolutionary dynamics, including time-dependent coexistence of cooperation and defection, systemwide shifts in the dominant strategy, and maturation in individual choices. Our results are robust to variations in network type and size, and strategy updating rules. Accounting for diverse strategic identities thus has far-reaching implications in the mathematical modeling of social games.

The energetic proximity of crystal electric field (CEF) to phonon excitations in rare-earth materials can lead to strong electron-phonon coupling, exotic behavior, and technologically useful properties. We present a temperature-, pressure-, and magnetic field-dependent Raman scattering study of ${\mathrm{Pr}}_2{\mathrm{O}}_3$ that reveals soft phonon mode behavior and anomalies associated with CEF excitations, which are indicative of strong phonon-CEF coupling. We also show that both an applied magnetic field and pressure induce a similar splitting of the doubly degenerate ${\mathrm{\Gamma }}_3$ crystal-field level, providing evidence for pressure-induced magnetostructural effects in ${\mathrm{Pr}}_2{\mathrm{O}}_3$. These results demonstrate the importance of low-lying CEF excitations and strong CEF-phonon coupling in governing the phases and properties of rare-earth materials.

Non-Hermitian skin effect and critical skin effect are unique features of non-Hermitian systems. In this work, we explore novel phenomena associated with the ${\mathbb{Z}}_2$ skin effect and critical skin effect in open quantum systems. For the open system with the corresponding damping matrix exhibiting ${\mathbb{Z}}_2$ skin effect, we identify the existence of helical damping, characterized by the evolution of relative particle number with exponentially and algebraically decreasing intervals distinguished by sharp wave fronts with opposite propagation directions. When the time-reversal symmetry is broken by adding perturbations, we find the occurrence of dynamical critical skin effect, which causes the disappearance of the helical damping in the thermodynamic limit although it can survive in small size systems. We also demonstrate the existence of anomalous critical skin effect when we couple two identical systems with ${\mathbb{Z}}_2$ skin effect. With the help of non-Bloch band theory, we unveil that the change of generalized Brillouin zone equation is the origin of critical skin effect.

Confined glasses and their anomalous interfacial rheology raise important questions in fundamental research and numerous practical applications. In this work, we study the influence of interfacial air nanobubbles on the free surface of ultrathin high-molecular-weight glassy polystyrene films immersed in water, in ambient conditions. In particular, we reveal the counterintuitive fact that a soft nanobubble is able to deform the surface of a rigid glass, forming a nanocrater with a depth that increases with time. By combining in situ atomic-force-microscopy measurements and a modified lubrication model for the liquidlike layer at the free surface of the glass, we demonstrate that the capillary pressure in the nanobubble together with the liquidlike layer at the free surface of the glass determine the spatiotemporal growth of the nanocraters. Finally, from the excellent agreement between the experimental profiles and the numerical solutions of the governing glassy thin-film equation, we are able to precisely extract the surface mobility of the glass. In addition to revealing and quantifying how surface nanobubbles deform immersed glasses, until the latter eventually dewet from their substrates, our work provides a novel, precise, and simple measurement of the surface nanorheology of glasses.

Fracton phases exhibit striking behavior which appears to render them beyond the standard topological quantum field theory (TQFT) paradigm for classifying gapped quantum matter. Here, we explore fracton phases from the perspective of defect TQFTs and show that topological defect networks—networks of topological defects embedded in stratified $3+1$-dimensional $(3+1\mathrm{D})$ TQFTs—provide a unified framework for describing various types of gapped fracton phases. In this picture, the subdimensional excitations characteristic of fractonic matter are a consequence of mobility restrictions imposed by the defect network. We conjecture that all gapped phases, including fracton phases, admit a topological defect network description and support this claim by explicitly providing such a construction for many well-known fracton models, including the X-cube and Haah's B code. To highlight the generality of our framework, we also provide a defect network construction of a fracton phase hosting non-Abelian fractons. As a byproduct of this construction, we obtain a generalized membrane-net description for fractonic ground states as well as an argument that our conjecture implies no topological fracton phases exist in $2+1$-dimensional gapped systems. Our paper also sheds light on techniques for constructing higher-order gapped boundaries of $3+1\mathrm{D}$ TQFTs.

Some deep conjectures about quantum gravity are closely related to the role of symmetries in the gravitational background, especially for quantum black holes. In this paper, we systematically study the theory of quantum information for a charged, chaotic system. We show how the quantum information in the whole system has been represented by its charge sectors, using the theory of quantum chaos and quantum error correction, with concrete examples in the context of the complex Sachdev-Ye-Kitaev model. We discuss possible implications for black-hole thought experiments and conjectures about quantum gravity in the dynamical setup. We believe this work will have potential applications from theories of quantum gravity to quantum simulation in quantum devices.

Solving optimization problems encoded in the ground state of classical-spin systems is a focus area for quantum computing devices, providing upper bounds to the unknown solution. To certify these bounds, they are compared to those obtained by classical methods. However, even if the quantum bound beats them, this says little about how close it is to the unknown solution. We consider the use of relaxations to the ground-state problem as a benchmark for the output of quantum optimizers. These relaxations are radically more informative because they provide lower bounds to the ground-state energy. The chordal branch and bound algorithm we present provides a series of systematically improving confidence regions where the ground-state energy provably lies. Interestingly, each step in the process requires only an effort polynomial in the system size. Additionally, the algorithm exploits the locality and sparsity of relevant Ising spin models in a systematic way. This yields certified solutions for many of the problems that are currently addressed by heuristic optimization algorithms more efficiently and for larger system sizes. We apply the method to verify the output of a D-Wave 2000Q device and identify instances where the annealer does not reach the ground-state energy and, more importantly, instances where it does, something impossible to do by means of standard variational approaches. Our work provides a flexible and scalable method for the verification of the outputs produced by quantum optimization devices.

Cooling methods and particle slowers as well as accelerators are basic tools for fundamental research and applications in different fields and systems. We put forward a generic mechanism to scale the momentum of a particle, regardless of its initial position and momentum, by means of a transient harmonic potential. The design of the time-dependent frequency makes use of a linear invariant and inverse techniques drawn from “shortcuts to adiabaticity.” The timing of the process may be decided beforehand, and its influence on the system evolution and final features is analyzed. We address quantum systems, but the protocols found are also valid for classical particles. Similar processes are possible as well for position scaling.

We develop a theoretical approach to “spontaneous stochasticity” in classical dynamical systems that are nearly singular and weakly perturbed by noise. This phenomenon is associated with a breakdown in the uniqueness of solutions for fixed initial data and underlies many fundamental effects of turbulence (unpredictability, anomalous dissipation, enhanced mixing). Based upon an analogy with statistical-mechanical critical points at zero temperature, we elaborate a renormalization group (RG) theory that determines the universal statistics obtained for sufficiently long times after the precise initial data are “forgotten.” We apply our RG method to solve exactly the “minimal model” of spontaneous stochasticity given by a 1D singular ordinary differential equation (ODE). Generalizing prior results for the infinite-Reynolds limit of our model, we obtain the RG fixed points that characterize the spontaneous statistics in the near-singular, weak-noise limit, determine the exact domain of attraction of each fixed point, and derive the universal approach to the fixed points as a singular large-deviation scaling, distinct from that obtained by the standard saddle-point approximation to stochastic path integrals in the zero-noise limit. We present also numerical simulation results that verify our analytical predictions, propose possible experimental realizations of the “minimal model,” and discuss more generally current empirical evidence for ubiquitous spontaneous stochasticity in Nature. Our RG method can be applied to more complex, realistic systems and some future applications are briefly outlined.

Based on a topological transition of the symmetry-protected topological phase (SPT), an interaction-induced topological charge pump (iTCP) is proposed with the symmetry-breaking parameter as a synthetic dimension. It implies that the phase boundary of the SPT is a topological obstruction, although iTCP and the gap closing singularity are stable for symmetry-breaking perturbations. As for the iTCP, an interaction is essential since the pumped charge is trivial for a noninteracting system. We have confirmed the bulk-edge correspondence for this iTCP using density matrix renormalization group for the Rice-Mele model with nearest-neighbor interactions. As for a realization in optical lattices, an interaction sweeping pump protocol is proposed as well.