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Identifying and mitigating unknown disturbances to complex systems poses a critical challenge in a wide range of disciplines. Here, the authors use machine learning to identify unknown disturbances made to unknown systems and a methodology to suppress these disturbances to recover the undisturbed system.
End-to-end learning in hybrid numerical models involves solving an optimization problem that integrates the model’s solver. In many fields, these solvers are written in low-abstraction programming languages that lack automatic differentiation. This work presents a practical approach to solving the optimization problem by efficiently approximating the gradient of the end-to-end objective function.
The authors investigate quantum entanglement in the hyperfine structure of the neutral hydrogen atom in thermal equilibrium with the cosmological microwave background radiation. They demonstrate that when the universe is around 80 billion years old, neutral hydrogen atoms begin to form entangled states, displaying a phenomenon known as entanglement sudden birth.
In-phase synchronization of laser arrays remains one of the most important open problems in laser science. This work utilizes the relationship between chiral symmetric tight-binding models and supersymmetry to engineer a near-uniform laser array with a superior far-field intensity scaling, extending the frontiers of laser technology.
A reliable characterization of x-ray pulses is critical to optimally exploit advanced photon sources, such as free-electron lasers. The authors present a method based on machine learning which improves the resolution and signal-to-noise ratio of the non-invasive spectral diagnostics available at European XFEL, and streamlines its operation.
High harmonics generation (HHG) is a promising way of investigating electronic structures and anisotropy in materials. The authors demonstrate the observation of HHG in simple structural material, hexagonal metal titanium, and experimentally clarified the anisotropy in the electronic states from the polarization dependence.
The hour-glass magnetic excitation spectrum is a universal feature of most cuprate high-temperature superconductors, yet the exact origins are still debated. Here, using inelastic neutron scattering techniques, the authors report hour-glass magnetic spectra in an oxygen-doped cobaltate La2CoO4+δ and discuss the potential link with charge stripes and the “diamond-shaped” high energy part of the hour-glass spectrum of this system.
A bottleneck for the analysis of data produced by angle-resolved photoemission spectroscopy (ARPES) is the size of the data related to spatial resolution. Building on earlier work, the authors present a data processing method that adopts unsupervised machine learning-based tools to improve the accuracy and efficiency when analysing data produced by nano-ARPES measurements.
Topological superconductivity is the holy grail for implementing fault-tolerant quantum computation. Here, the authors show that for a superconducting monolayer Td−MoTe2 characterized by the Ising plus in-plane spin-orbit coupling, applying an in-plane magnetic field can drive it to a topological superconductor.
The authors propose a method to detect anomalies in dynamic networks by using community structure as a baseline for normal behavior: the model flags anomalies as irregular connections while tracking structural changes. In football player transfers, it reveals patterns tied to club wealth, nationality, and unexpected transactions across communities.
The 30-years development of quantum cascade lasers has established them as a go-to source of coherent radiation in the Mid-IR and THz ranges. In this comment, the authors guide the reader through the landmark achievements of this technology, from a lab curiosity to a mature technology adopted by research groups and companies.
Topological invariants are critical in characterizing higher-order topological insulators. In this work, the authors show how to define a multipole winding number that can capture the bulk-corner correspondence, including boundary obstructed topological phases. An experimental proposal complements the theoretical one.
A defining characteristic of non-trivial topological materials is the bulk-boundary correspondence, and the majority of research activities has tended to centre around the surface states. Here, the authors conduct electrical transport measurements on β-Ag2Se observing anomalies in the magnetoresistance measurements, which they contend has a direct connection to the non-trivial topological nature of β-Ag2Se.
Spectroscopic ellipsometry, capable of measuring the thickness of thin films with an accuracy of angstroms, has been widely used both in research and commercially. Here, the authors theoretically and experimentally demonstrate a unique variant of spectroscopic ellipsometry utilizing frequency division multiplexed lasers of different wavelengths.
Atomically thin materials offer unique opportunities for controlling electronic properties layer by layer. This study introduces a monolithically grown twistronic stack of monolayer and bilayer graphene, revealing that structural asymmetry can induce a band gap in bilayer graphene without external fields.
Quantum spin liquids are materials predicted to be absent of magnetic ordering at low temperature, giving rise to fractionalised electronic states, but conclusive experimental evidence is still absent. Here, the authors conduct angular dependent torque measurements on the candidate spin liquid material RuI3 and, through a comparison of experimental and theoretical results, provide evidence indicating the presence of frustrated magnetic interactions in the system.
The coupling of an exciton to an electromagnetic field leads to the formation of an exciton polariton and in transition metal dichalcogenides specifically, they might be candidates for room temperature Bose-Einstein condensation. Here, the authors observe excitons at the onset of polaritonic mode formation in the confinement of nanometer thin and monolayer WSe2. Excitonic intensities were controlled locally by nanosized modifications to the material’s geometry.
Quantum error correction produces an enormous amount of data about the quantum system, including information about whether an uncorrectable error is likely. In this work the authors analyse a new decoder that can abort when decoding is deemed too difficult, yielding improved performance overall.
The charge density wave (CDW) formation mechanisms in 2D and quasi-2D systems are still highly debated. Here, the authors combine time-resolved ARPES and ab initio calculations to map the free energy functional in the prototypical CDW compound 1T-TaSe2 concluding that the CDW state is driven by structural rather than electronic instabilities.
Flat bands states can be written, in general, as localized states that can couple by placing impurities at the overlapping regions, when present. The authors develop an analytic framework to derive impurity states in a diamond chain with magnetic flux and find an exotic behavior of these states characterized by a half-integer winding number.
