Reviews & Analysis

The standard Hamiltonian approach to quantum field theory violates Poincaré invariance, leading to predictions with artificial dynamical effects and potentially obscuring the fundamental description of a physical system. This Perspective explains how such issues are avoided by using light-front Hamiltonian quantization.

Active matter encompasses various non-equilibrium systems in which individual constituents convert energy into non-conservative forces or motion at the microscale. This Review provides an elementary introduction to the role of topology in active matter through experimentally relevant examples.

Minimizing the energy of the Ising model is a prototypical combinatorial optimization problem, ubiquitous in our increasingly automated world. This Review surveys Ising machines — special-purpose hardware solvers for this problem — and examines the various operating principles and compares their performance.

Polaritonics is the physics of strongly coupled light–matter states that studies condensates and superfluids of bosonic quasiparticles in solid-state systems. Coherent flows of exciton–polaritons can be used for classical and quantum information processing, offering advantages of full optical control and read-out.

Electric-double-layer transistors and ionic field-effect transistors enable continuous tuning of carrier densities in 2D superconductors, which are essential for studying novel quantum phenomena and finding new high-temperature superconductors. This Review summarizes recent advances and future development paths for electric-field-gated superconductivity in various ultrathin superconducting materials, including iron-based superconductors, transition-metal dichalcogenides, honeycomb bilayer superconductors and cuprates.

Finding the most appropriate machine learning algorithm for the analysis of any given scientific dataset is currently challenging, but new machine learning benchmarks for science are being developed to help.

Multi-messenger observations of gravitational waves and electromagnetic radiation directly probe the synthesis of heavy elements in the Universe. This Review summarizes recent results and charts future challenges and opportunities for identifying the astrophysical origin of roughly half of the elements heavier than iron.

New approaches to integrate high-dimensional recordings of brain activity with single-neuron resolution with simultaneous recordings of natural animal behaviour enable the study of brain-wide activity in small animals including worms, flies and fish during behaviours and decision-making. This Review surveys experimental and theoretical approaches that have opened this area of systems neuroscience.

Mastering thermal conductivities of materials under pressure is extremely important for managing thermal processes, understanding the thermal transport mechanisms and for potential technological applications. This Review surveys the progresses in technique developments, research results and scientific implications in this field.

Graphene oxide (GO) has attracted intensive research interest, owing to remarkable physicochemical properties. Nevertheless, its high chemical reactivity and low stability may lead to uncontrolled GO derivatives. The chemistry of GO can be controlled by selective derivatization of the oxygenated groups and C=C bonds and by appropriate characterization.

The observation of gravitational waves emitted in the merger of neutron stars and the observations of X-rays emitted by hotspots on their surfaces are beginning to reveal nuclear physics insights about these compact objects.

Magnetic reconnection explosively releases stored magnetic energy in astrophysical plasmas. Thanks to advances in observations, exascale computing and multiscale experiments, it will be possible to solve outstanding physics problems, including the immense separation between global and dissipation scales, reconnection onset and particle acceleration.

Much of the rich phenomenology of active matter can be traced back to violations of time-reversal symmetry and departure from Boltzmann statistics. This Review disentangles these nonequilibrium signatures for interacting and dilute systems, in the presence of obstacles and external potentials.

Quantum photonics offers an integrated and scalable approach to quantum information processing and communication. This article summarizes the state of the art and provides an outlook on future challenges and opportunities for quantum photonics based on 2D materials.

Spintronic properties of layered materials combining magnetism and strong spin–orbit coupling can be tailored by proper optimization of chemical interactions and structural material symmetries. This Review draws a route to achieving best performing material design for reaching the upper limit of spin–orbit torque efficiency in switching magnetization.

Photonics is one of the key platforms for emerging quantum technologies, but its full potential can only be harnessed by exploiting miniaturization via on-chip integration. This Roadmap charts new directions and discusses the challenges associated with the hybrid integration of a variety of materials, devices and components.

In 2021, the most precise measurement of the muon’s anomalous magnetic moment and a new high-precision lattice quantum chromodynamics calculation have in turn kindled, then dimmed, hopes for seeing signs of new physics. State-of-the-art calculations, made possible by a series of recent advances, will be key to understanding these conflicting results.

Metamaterials enable precise tailoring of light–matter interactions. This Review discusses recent developments in the use of metamaterials for imaging.

Topological insulators are unique materials giving rise to unconventional quantum phenomena. This Technical Review discusses how various physics effects can only be observed in devices carefully fabricated to address them, including topological superconductivity, quantum anomalous Hall states, spintronic functionalities and topological mesoscopic physics.

Peoples’ movements are linked with the spread of epidemics — but not always in simple ways. In the past two years, new datasets and analyses have shed fresh light on how to relate mobility and contagion.