Superradiance is the anomalous radiance describing coherent photon emission from a gas. It plays a crucial role in atomic physics, quantum mechanics and astrophysics. Because the intensity of superradiant light beams is proportional to the number of particles squared, superradiance is also at the core of today’s most powerful light sources. Superradiant emission is intuitively expected when the distance

Quantum measurement remains a puzzle through its stormy history from the birth of quantum mechanics to state-of-the-art quantum technologies. Two complementary measurement schemes have been widely investigated in a variety of quantum systems: von Neumann’s projective ‘strong’ measurement and Aharonov’s weak measurement. Here, we report the observation of a weak-to-strong measurement transition in a

The flat bands that appear in some twisted van der Waals heterostructures provide a setting in which strong interactions between electrons lead to a variety of correlated phases1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20. In particular, heterostructures of twisted double bilayer graphene host correlated insulating states that can be tuned by both the twist angle and an external electric field11

Natural soils are host to a high density1 and diversity2 of microorganisms, and even deep-earth porous rocks provide a habitat for active microbial communities3. In these environments, microbial transport by disordered flows is relevant for a broad range of natural and engineered processes, from biochemical cycling to remineralization and bioremediation4,5,6,7. Yet, how bacteria are transported and

Although quantum mechanics is essential to understand microscopic systems, it has little effect on heavier objects. Experiments have now put strict constraints on theories that use gravity to explain the absence of large-scale quantum effects.

Roger Penrose proposed that a spatial quantum superposition collapses as a back-reaction from spacetime, which is curved in different ways by each branch of the superposition. In this sense, one speaks of gravity-related wave function collapse. He also provided a heuristic formula to compute the decay time of the superposition—similar to that suggested earlier by Lajos Diósi, hence the name Diósi–Penrose

Hydrogen metallization under stable conditions is a substantial step towards the realization of the first room-temperature superconductor. Recent low-temperature experiments1,2,3 report different metallization pressures, ranging from 360 GPa to 490 GPa. In this work, we simulate the structural properties and vibrational Raman, infrared and optical spectra of hydrogen phase III, accounting for proton

Glass is inherently unstable to crystallization. However, how this transformation occurs while the dynamics in the glass stay frozen at the particle scale is poorly understood. Here, through single-particle-resolved imaging experiments, we show that due to frozen-in density inhomogeneities, a soft colloidal glass crystallizes via two distinct pathways. In the poorly packed regions of the glass, crystallinity

Hybrid quantum materials allow for quantum phases that otherwise do not exist in nature1,2. For example, a one-dimensional topological superconductor with Majorana states bound to its ends can be realized by coupling a semiconductor nanowire to a superconductor in the presence of a strong magnetic field3,4,5. However, the applied magnetic fields are detrimental to superconductivity, and constrain device

The properties of anyons — two-dimensional particles that are neither fermions nor bosons — have been directly measured in a quantum Hall interferometer.

Anyons are quasiparticles that, unlike fermions and bosons, show fractional statistics when two of them are exchanged. Here, we report the experimental observation of anyonic braiding statistics for the ν = 1/3 fractional quantum Hall state by using an electronic Fabry–Perot interferometer. Strong Aharonov–Bohm interference of the edge mode is punctuated by discrete phase slips that indicate an anyonic

A remarkable property of quantum mechanics in two-dimensional space is its ability to support ‘anyons’, particles that are neither fermions nor bosons. Theory predicts that these exotic excitations can exist as bound states confined near topological defects, such as Majorana zero modes trapped in vortices in topological superconductors. Intriguingly, in the simplest cases the non-trivial phase that

Wolfgang Pauli introduced the Bohr magneton as a fundamental unit of magnetic moment during an effort to find a quantum basis for magnetism, as Davide Castelvecchi recounts.

The First Plasma discharge in the ITER tokamak is expected for 2025 with deuterium–tritium plasma operation ten years later. We spoke with ITER’s Director-General, Bernard Bigot, and Tim Luce, head of ITER’s Science & Operations Department, about the current status of the project and potential future directions in fusion research.

Many-body quantum systems can exhibit a striking degree of symmetry unparallelled in their classical counterparts. In real materials SU(N) symmetry is an idealization, but this symmetry is pristinely realized in fully controllable ultracold alkaline-earth atomic gases. Here, we study an SU(N)-symmetric Fermi liquid of 87Sr atoms, where N can be tuned to be as large as 10. In the deeply degenerate regime

Copper oxide high-TC superconductors possess a number of exotic orders that coexist with or are proximal to superconductivity. Quantum fluctuations associated with these orders may account for the unusual characteristics of the normal state, and possibly affect the superconductivity1,2,3,4. Yet, spectroscopic evidence for such quantum fluctuations remains elusive. Here, we use resonant inelastic X-ray

The influence of geometry on the local and global packing of particles is important to many fundamental and applied research themes, such as the structure and stability of liquids, crystals and glasses. Here we show by experiments and simulations that a binary mixture of hard-sphere-like nanoparticles crystallizing into a MgZn2 Laves phase in bulk spontaneously forms icosahedral clusters in slowly

As the construction of the ITER tokamak enters its next phase — the machine assembly — now is a good time for a recap of the history and current status of nuclear fusion research.

The pace and unpredictability of evolution are critically relevant in a variety of modern challenges, such as combating drug resistance in pathogens and cancer, understanding how species respond to environmental perturbations like climate change and developing artificial selection approaches for agriculture. Great progress has been made in quantitative modelling of evolution using fitness landscapes

Self-organization is a prerequisite of biological complexity. At the population level, it amounts to spontaneously sorting different individuals through space and time. Here, we reveal a simple mechanism by which different populations of motile cells can self-organize through a reciprocal control of their motilities. We first show how the reciprocal activation of motility between two populations of

Two-dimensional materials offer an exciting platform that enables the creation of van der Waals heterostructures with rich functions and intriguing physical properties that stem from different band alignments and diverse interlayer interactions. However, further exploration of two-dimensional van der Waals heterostructures is hindered by the limited coupling strength and lack of efficient methods for

When a semiconductor is embedded inside a microcavity, infrared photons have been shown to bind electrons and holes together as excitons. This result opens the door for quantum material engineering based on light–matter interactions.

The discussion of the quantum mechanical Wigner’s friend thought experiment has regained intensity. Recent theoretical results and experimental tests restrict the possibility of maintaining an observer-independent notion of measurement outcomes.

In contrast to interband excitons in undoped quantum wells, doped quantum wells do not display sharp resonances due to excitonic bound states. The effective Coulomb interaction between electrons and holes in these systems typically leads to only a depolarization shift of the single-electron intersubband transitions1. Non-perturbative light–matter interaction in solid-state devices has been investigated

Does quantum theory apply at all scales, including that of observers? New light on this fundamental question has recently been shed through a resurgence of interest in the long-standing Wigner’s friend paradox. This is a thought experiment addressing the quantum measurement problem—the difficulty of reconciling the (unitary, deterministic) evolution of isolated systems and the (non-unitary, probabilistic)

Ultralight axion-like particles are well-motivated dark matter candidates, naturally emerging from theories of physics at ultrahigh energies. Here we report the results of a direct search for electromagnetic interactions of axion-like dark matter in the mass range that spans three decades from 12 peV to 12 neV. The detection scheme is based on a modification of Maxwell’s equations in the presence of

In 1929, Felix Bloch suggested that the paramagnetic Fermi sea of electrons should make a spontaneous transition to a fully magnetized state at very low densities, because the exchange energy gained by aligning the spins exceeds the enhancement in the kinetic energy1. However, experimental realizations of this effect have been hard to implement. Here, we report the observation of an abrupt, interaction-driven

The quantum anomalous Hall effect1,2 is a fundamental transport response of a topological insulator in zero magnetic field. Its physical origin is a result of an intrinsically inverted electronic band structure and ferromagnetism3, and its most important manifestation is the dissipationless flow of chiral charge currents at the edges of the system4, a property that has the potential to transform future

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Many unconventional superconductors exhibit a common set of anomalous charge transport properties that characterize them as ‘strange metals’, which provides hope that there is a single theory that describes them1,2,3. However, model-independent connections between the strange metals and superconductivity have remained elusive. Here, we show that the Hall effect of the unconventional superconductor

Magnons are collective spin excitations in crystals with long-range magnetic order. The emergent van der Waals magnets1,2,3 provide a highly tunable platform to explore magnetic excitations in the two-dimensional limit with intriguing properties, manifesting from their honeycomb lattice structure and switchable magnetic configurations. Here, we report the direct observation of two-dimensional magnons

Noise is the central obstacle to building large-scale quantum computers. Quantum systems with sufficiently uncorrelated and weak noise could be used to solve computational problems that are intractable with current digital computers. There has been substantial progress towards engineering such systems1,2,3,4,5,6,7,8. However, continued progress depends on the ability to characterize quantum noise reliably

In most unconventional and high-temperature superconductors, superconductivity emerges as a nearby symmetry-breaking phase is suppressed by chemical doping or pressure1,2,3,4,5,6,7. This has led to the belief that the fluctuations associated with the symmetry-breaking phase are beneficial, if not responsible, for the superconducting pairing8,9. A direct test to verify this hypothesis is to observe

The respiratory tract is protected by mucus, a complex fluid transported along the epithelial surface by the coordinated beating of millions of microscopic cilia, hence the name of mucociliary clearance. Its impairment is associated with all severe chronic respiratory diseases. Yet, the relationship between ciliary density and the spatial scale of mucus transport, as well as the mechanisms that drive

The radiation-pressure coupling between two harmonic oscillators has been used in optomechanics for breakthrough experiments in the control and detection of mechanical displacement. Used primarily in optomechanics, there have been few reports of exploiting such a type of interaction in other platforms. Here, we engineer two superconducting LC circuits coupled by a strong photon-pressure interaction

Most physical and other natural systems are complex entities that are composed of a large number of interacting individual elements. It is a surprising fact that they often obey the so-called scaling laws that relate an observable quantity to a measure of the size of the system. Here, we describe the discovery of universal superlinear metabolic scaling laws in human cancers. This dependence underpins

The persistent under-representation of Black physicists is a systemic problem that requires will, money and long-term commitment to be solved.

Giacomo Prando summarizes the troubled history of the radian, a unit with the odd property of appearing and disappearing seemingly at will in dimensional formulas.

A mooted advantage of high-dimensional states is their robustness to noise, yet their fragility in noisy channels has hindered their deployment. A demonstration shows how to exploit entanglement to restore quantum correlations lost in transmission.

The transfer of quantum information through a noisy environment is a central challenge in the fields of quantum communication, imaging and nanophotonics. In particular, high-dimensional quantum states of light enable quantum networks with significantly higher information capacities and noise robustness as compared with qubits. However, although qubit entanglement has been distributed over large distances

The Casimir force was predicted in 1948 as a force arising between macroscopic bodies from the zero-point energy. At finite temperatures, it has been shown that a thermal Casimir force exists due to thermal rather than zero-point energy and there are a growing number of experiments that characterize the effect at a range of temperatures and distances. In addition, in the rapidly evolving field of cavity

An exactly solvable model for superconductivity includes two crucial features of the cuprates and sheds light on unexplained experiments.

Because the cuprate superconductors are doped Mott insulators, it would be advantageous to solve even a toy model that exhibits both Mottness and superconductivity. We consider the Hatsugai–Kohmoto model1,2, an exactly solvable system that is a prototypical Mott insulator. Upon either doping or reducing the interaction strength, our exact calculations show that the system becomes a non-Fermi liquid

There is a limit to the miniaturization of every process, and for charge transport this is realized by the coupling of two single discrete energy levels at the atomic scale. In superconductors, Yu–Shiba–Rusinov (YSR) states are such levels. Here, we place a magnetic impurity on the tip of a scanning tunnelling microscope (YSR-STM) and use it to demonstrate sequential tunnelling of electrons between

Bilayer graphene has been predicted to host a moiré miniband with flat dispersion if the layers are stacked at specific twist angles known as the ’magic angles’1,2. Recently, twisted bilayer graphene (tBLG) with a magic angle twist was reported to exhibit a correlated insulating state and superconductivity3,4, where the presence of the flat miniband in the system is thought to be essential for the

Tunnelling across superconducting junctions proceeds by a rich variety of processes, which transfer single electrons, Cooper pairs or even larger numbers of electrons by multiple Andreev reflections. Photon-assisted tunnelling combined with the venerable Tien–Gordon model has long been a powerful tool to identify tunnelling processes between superconductors. Here, we probe superconducting tunnel junctions

Much of modern metrology and communication technology encodes information in electromagnetic waves, typically as an amplitude or phase. Although current hardware can perform near-ideal measurements of photon number or field amplitude, the ability to perform an ideal phase measurement is still lacking, even in principle. In this work, we implement a single-shot canonical phase measurement on a one-photon

In many chemical reactions, the transformation from reactants to products is mediated by transient intermediate complexes. For gas-phase reactions involving molecules with a few atoms, these complexes typically live on the order of 10 ps or less before dissociating, and are therefore rarely influenced by external processes. Here, we demonstrate that the transient intermediate complex K2Rb2*, formed

The nature of the pseudogap phase of cuprates remains a major puzzle1,2. One of its signatures is a large negative thermal Hall conductivity3, whose origin is as yet unknown. This is observed even in the undoped Mott insulator La2CuO4, in which the charge carriers are localized and therefore cannot be responsible. Here, we show that the thermal Hall conductivity of La2CuO4 is roughly isotropic; that

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Weyl semimetals in three-dimensional crystals provide the paradigm example of topologically protected band nodes. It is usually taken for granted that a pair of colliding Weyl points annihilate whenever they carry opposite chiral charge. In stark contrast, here we report that Weyl points in systems that are symmetric under the composition of time reversal with a π rotation are characterized by a non-Abelian

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

This month, a Focus issue highlights recent developments in fundamental research on superconductivity.

When you start tearing a piece of aluminium foil apart, you create dislocations in the material. Suhas Eswarappa Prameela and Tim Weihs recount the story of the Burgers vector that is now an indispensable tool for describing dislocations.

Squeezed light is useful for metrology and quantum information. An optomechanical squeezed light source that works at room temperature will facilitate the technological applications of quantum light.

Topological superconductivity can emerge from the combination of conventional superconductivity in a metal and strong spin–orbit coupling in a semiconductor when they are made into a hybrid device. The most exciting manifestation of topological superconductivity is the Majorana zero modes that are predicted to exist at the ends of the proximatized nanowires. In this Perspective, we review the evidence

Squeezed light—light with quantum noise lower than shot noise in some quadratures and higher in others—can be used to improve the sensitivity of precision measurements. In particular, squeezed light sources based on nonlinear optical crystals are being used to improve the sensitivity of gravitational wave detectors. In optomechanical squeezers, the radiation-pressure-driven interaction of a coherent

The Bardeen–Cooper–Schrieffer theory of superconductivity and the Landau–Fermi liquid theory form the basis of our current understanding of conventional superconductors and their parent non-superconducting phases. However, some exotic superconductors do not conform to this physical picture but instead feature an unusual ‘normal’ state that is not a Fermi liquid. One explanation of this unusual behaviour

In order to understand the emergence of superconductivity it is useful to study the reverse process and identify the various pathways that lead to its destruction. One way is to increase the amount of disorder, as this leads to an increase in Coulomb repulsion that overpowers the attractive interaction responsible for Cooper pair formation. A second pathway—applicable to uniformly disordered materials—is

Near-term quantum computations are susceptible to noise that — left uncorrected — can destroy the correlations responsible for quantum computational speedups. New work develops tools for bolstering the noise resilience of these speedups.