We examine energetic electron transport in Earth’s outer radiation belt, presenting a mechanism for rapid (nondiffusive) radial transport. This process relies on electron crossings of an asymmetric separatrix in slow-fast Hamiltonian system, occurring in Earth’s dayside magnetosphere due to interactions with the interplanetary magnetic field. The resulting asymmetry quickly destroys adiabatic invariant through geometric jumps, driving exponential phase-space mixing and enhancing radial transport of $\gtrsim 1\mathrm{MeV}$ electrons during geomagnetically quiet conditions.

Despite the fundamentally different dissipation mechanisms, many laws and phenomena of classical turbulence equivalently manifest in quantum turbulence. The Reynolds law of dynamical similarity states that two objects of the same geometry across different length scales are hydrodynamically equivalent under the same Reynolds number, leading to a universal drag coefficient law. In this Letter we confirm the existence of a universal drag law in a superfluid wake, facilitated by the nucleation of quantized vortices. We numerically study superfluid flow across a range of Reynolds numbers for the paradigmatic classical hard wall and the Gaussian obstacle, popular in experimental quantum hydrodynamics. In addition, we provide a feasible method for measuring superfluid drag forces in an experimental environment using control volumes.

We consider the diffusive spin dynamics of a 2D electron gas with spin-orbit coupling confined within a grid of narrow channels. We show that the lifetime of certain spin distributions in such grids greatly exceeds that in an unconfined 2D electron gas and diverges as the channel width approaches zero. Such persistent spin grids are akin to spin crystals and occur if the electron spin orientation remains invariant after diffusion around the grid plaquette. We establish a topological ${\mathbb{Z}}_2$ classification for persistent spin grids and show how the grids with spatially varying parameters can simulate non-Abelian lattice gauge theories.

The reduced Coulomb screening in single-layer (1L) transition metal dichalcogenides (TMDs) offers an ideal setting to explore excitonic many-body correlations. The interactions between excitons result in intra- and intervalley biexcitonic multiparticle states, whose contributions to the nonlinear optical response have remained elusive so far. Here, by using helicity-resolved transient absorption spectroscopy with sub-10 fs temporal resolution combined with a microscopic theory based on the excitonic Bloch equations we are able to unambiguously disentangle the contribution of two particle exciton and four particle biexciton correlations to the coherent optical response of $1\mathrm{L}\text{−}{\mathrm{WSe}}_2$ semiconductor. Upon resonant excitation of valley-polarized A exciton population we observe competing excitation-induced energy shift of the A exciton transition along with a coherent gain in the pumped valley and an instantaneous formation of an additional absorption peak in the unpumped valley, which we attribute to the effect of bound intervalley biexcitons. An excellent agreement between experimental results and calculations allows us to deepen understanding of many-body effects in 1L-TMDs, which is crucial for the development of excitonic and valleytronics devices.

This Letter details the role of reduced hydrodynamic mix in achieving the first fusion plasma to satisfy the Lawson criterion for ignition. Using novel 3D measurements of the temperature and density of the burning deuterium-tritium plasma across a series of experiments, we demonstrate that hydrodynamic mixing from small-scale capsule defects was a key degradation mechanism inhibiting ignition. A series of five layered deuterium-tritium experiments using 1.9 MJ of laser energy demonstrates a $2\times$ reduction of the thermonuclear yield when a lower quality capsule, typical of preignition experiments, is used. Radiation hydrodynamic calculations consistent with the observed mix profile show that the mixed fuel’s reduced compression and increased radiative loss explain the yield reduction. A hydroscaling argument suggests that a $\sim 3\mathrm{MJ}$ laser would be needed to reach ignition with such a capsule, well beyond the current capabilities of high energy laser systems. As such, this Letter gives critical insight into the physics of mix in self-heated fusion plasmas and establishes a foundation to evaluate capsule quality needs of future inertial fusion designs that aim at ignition and high gain.

The low kinetic friction between ice and numerous counterbodies is commonly attributed to an interfacial water layer, which is believed to originate from preexisting surface water or from melt water induced by high contact pressures or frictional heat. However, even the currently leading theory of frictional melting appears to defy direct experimental verification. Here we present molecular simulations of ice interfaces that reveal that ice surfaces liquefy without melting thermodynamically but predominantly by cold, displacement-driven amorphization. Despite effective self-lubrication, very small ice friction is found to require water to slip past a hydrophobic counterface—or an excess amount of water, produced by, e.g., extreme sliding velocities.

Quantum randomness can be certified from probabilistic behavior demonstrating Bell nonlocality or Einstein-Podolsky-Rosen steering, leveraging outcomes from uncharacterized devices. However, in standard spot-checking protocols, such nonlocal correlations are not always sufficient for this task, necessitating the identification of required minimum quantum resources. In this Letter, we focus on the bipartite scenario and provide the necessary and sufficient condition for nonzero certified randomness under any arbitrary but fixed input, formulated in terms of measurement incompatibility. Further, we develop practical approaches to detect it. Firstly, we show that the steering-based randomness can be certified if and only if the correlations arise from a measurement compatibility structure that is not isomorphic to a hypergraph containing a star subgraph. In such a structure, the central measurement is individually compatible with the measurements at branch sites, ruling out the possibility of certified randomness in the central measurement outcomes. Subsequently, we generalize this result to the Bell scenario, proving that the violation of any chained Bell inequality involving a finite number of inputs and outputs excludes such a compatibility structure, thereby validating all chained inequalities as credible witnesses for randomness certification. Our results point out the role of an incompatibility structure in generating random numbers, offering a way to identify minimum quantum resources for the task.

Quantum many-body scars are eigenstates in nonintegrable isolated quantum systems that defy typical thermalization paradigms, violating the eigenstate thermalization hypothesis and quantum ergodicity. We identify exact analytic scar solutions in a $2+1$ dimensional lattice gauge theory in a quasi-1D limit as zero-magic resource stabilizer states. Our results also highlight the importance of magic resources for gauge theory thermalization, revealing a connection between computational complexity and quantum ergodicity.

We prove an upper bound on long-range distillable entanglement in $D$ spatial dimensions. Namely, it must decay faster than $1/r$, where $r$ is the distance between entangled regions. For states that are asymptotically rotationally invariant, the bound is strengthened to $1/r^D$. We then find explicit examples of quantum states with decay arbitrarily close to the bound. In one dimension, we construct free fermion Hamiltonians with nearest neighbor couplings that have these states as ground states. Curiously, states in conformal field theory are far from saturation, with distillable entanglement decaying faster than any polynomial.

Equilibrium properties of many-body systems with a large number of degrees of freedom are generally expected to be described by statistical mechanics. Such expectations are closely tied to the observation of thermalization, as manifested through equipartition in time-dependent observables, which takes place both in quantum and classical systems but may look very different in comparison. By studying the dynamics of individual lattice site populations in ultracold bosonic gases, we show that the process of relaxation toward equilibrium in a quantum system can be orders of magnitude faster than in its classical counterpart. Classical chaos quantifiers reveal that this is due to a wave packet in a quantum system being able to escape regions of inefficient classical transport by a mechanism akin to tunneling. Since the presented phenomenon takes place in a broad parameter range and persists in weakly disordered systems, we expect that it occurs in a variety of many-body systems and is amenable to direct experimental verification in state-of-the-art quantum simulation platforms.

Despite the significant progress in superconducting quantum computation over the past years, quantum state measurement still lags nearly an order of magnitude behind quantum gate operations in speed and fidelity. The main challenge is that the strong coupling and readout signal used to probe the quantum state may also introduce additional channels which may cause qubit state transitions. Here, we design a novel architecture to implement the long-sought longitudinal interaction scheme between qubits and resonators. This architecture not only provides genuine longitudinal interaction by eliminating residual transversal couplings, but also introduces proper nonlinearity to the resonator that can further minimize decay error and measurement-induced excitation error. Combined with the multilevel readout protocol, we achieved a measurement fidelity of 99.8% in 202 ns without requiring any first-stage amplification. This highlights its potential as a highly promising architecture for superconducting qubit measurement.

The high-temperature plasma in the solar interior generates stochastic gravitational waves (GWs). Owing to its significance as the primary source of high-frequency GWs in the Solar System, we reexamine this phenomenon by highlighting some physical processes, including the contribution of macroscopic hydrodynamic fluctuations. Our analysis builds upon several studies of axion emission from the Sun, particularly in relation to the treatment of plasma effects. The resulting GW spectrum is comparable to many well-motivated early-Universe signals, yet orders of magnitude below the current sensitivities of axion helioscopes such as (Baby)IAXO.

In this Letter, we consider effective field theories for light fields transforming under the fundamental or adjoint representation of a continuous group. Assuming tree-level completions, we demonstrate that, in the presence of gravity, crossing symmetry combined with twice-subtracted sum rules leads to constraints on the irreducible representations that the ultraviolet degrees of freedom must populate. A spectrum is allowed only if its low energy projection contains the graviton pole. Beautifully, the graviton pole is the anchor of our argument, not an obstruction.

The Kibble-Zurek (KZ) mechanism renders a theoretical framework for elucidating the formation of topological defects across continuous phase transitions. Nevertheless, it is not immediately clear whether the KZ mechanism applies to topological phase transitions. The direct experimental study for such a topic is hindered by quenching a certain parameter over orders of magnitude in topological materials. Instead, we investigate the KZ behavior across topological transitions of a Chern band in two-dimensional (2D) optical Raman lattices with quantum gases. Defined as the defects, excitation density is reconstructed via measuring the spin wave functions, with which the power-law scaling of total excitation density is extracted and such scaling could be interpreted within the KZ framework. Our work has heralded the commencement of experimentally exploring the KZ mechanism of the topological phase transitions.

Quantum synchronization has been a subject of intensive research in the last decade. In this Letter, we propose a quantum Liénard system whose classical equivalent features two limit cycles to one of which the system will converge. In the quantum case, both limit cycles coexist in a single steady state. Each of these limit cycles localizes to a distinct phase if coupled to an external drive: one quantum state can thus be assigned two phases. Furthermore, coupling two such oscillators leads to the simultaneous appearance of synchronization and a synchronization blockade. To shed light on this apparent paradoxical result, we introduce finer measures of quantum synchronization.

Topological defects and textures play crucial roles in fundamental physics and modern information science. Torons are a class of three-dimensional (3D) chiral topological structures with both skyrmionic quasiparticle textures and monopole point defects, so far only observed in liquid crystals with both polar and nonpolar symmetry. Here, we construct torons with the photonic spin of vector structured light and demonstrate the topological phase transitions among diverse 3D topological states: torons, hopfions, skyrmioniums and monopole pairs. We can also continually tune the toron’s chirality and monopole’s helicity. The generation of photonic torons opens a platform for studying nontrivial light-matter interaction and topological informatics.