Review Articles

The discovery of spin-triplet Cooper pairs at superconductor/ferromagnet interfaces provides a route for combining superconducting and magnetic orders. Recent advances and challenges in the field of superconducting spintronics are now reviewed.

The task of integrating information into the framework of thermodynamics dates back to Maxwell and his infamous demon. Recent advances have made these ideas rigorous—and brought them into the laboratory.

Statistical mechanics is adept at describing the equilibria of quantum many-body systems. But drive these systems out of equilibrium, and the physics is far from clear. Recent advances have broken new ground in probing these equilibration processes.

Exciton–polaritons, resulting from the light–matter coupling between an exciton and a photon in a cavity, form Bose–Einstein-like condensates above a critical density. Various aspects of the physics of exciton–polariton condensates are now reviewed.

The superconducting energy gap is perhaps the best-known of the spectral gaps in a superconductor, but there are many other types, including density waves and the mysterious pseudogap. This Review Article surveys what angle-resolved photoemission spectroscopy has revealed about the various gaps.

Understanding the physics of two-dimensional materials beyond graphene is of both fundamental and practical interest. Recent theoretical and experimental advances uncover the interplay between real spin and pseudospins in layered transition metal dichalcogenides.

There are good reasons to consider nonlocality to be the defining feature of quantum mechanics, but stronger nonlocal correlations than those predicted by quantum theory could exist, which raises the intriguing question of what lies beyond.

Testing the limits of the quantum mechanical description of nature has become a subject of intense experimental interest. Recent advances in investigating macroscopic quantum superpositions are pushing these limits.

Starting with wave-particle duality, experiments with light have played a major role in the development of quantum theory. Advances in photonic technologies allow for improved tests of quantum complementarity, delayed-choice and nonlocality.

Nematic order in the iron-based superconductors breaks the symmetry between the x and y directions in the Fe plane. Beyond this, however, there is little consensus on how nematic order arises and whether it has an effect on superconductivity. This Review discusses the current theoretical and experimental state of the field.

Surface-plasmon polaritons are hybrid particles that result from strong coupling between light and collective electron motion on the surface of a metal. This Review presents an overview of the quantum properties of surface plasmons, their role in controlling light–matter interactions at the quantum level and potential applications.

Could biological systems have evolved to find the optimal quantum solutions to the problems thrown at them by nature? This Review presents an overview of the possible quantum effects seen in photosynthesis, avian magnetoreception and several other biological systems.

Experimental progress in controlling and manipulating trapped atomic ions has opened the door for a series of proof-of-principle quantum simulations. This article reviews these experiments, together with the methods and tools that have enabled them, and provides an outlook on future directions in the field.

Quantum optics has played an important role in the exploration of foundational issues in quantum mechanics, and in using quantum effects for information processing and communications purposes. Photonic quantum systems now also provide a valuable test bed for quantum simulations. This article surveys the first generation of such experiments, and discusses the prospects for tackling outstanding problems in physics, chemistry and biology.

Experiments with ultracold quantum gases provide a platform for creating many-body systems that can be well controlled and whose parameters can be tuned over a wide range. These properties put these systems in an ideal position for simulating problems that are out of reach for classical computers. This review surveys key advances in this field and discusses the possibilities offered by this approach to quantum simulation.

Vast amounts of data are available about complex technological systems and how we use them. These data provide the basis not only for mapping out connectivity patterns, but also for the study of dynamical phenomena, including epidemic outbreaks and routing of information through computer networks. This article reviews the fundamental tools for modelling such dynamical processes and discusses a number of applications.

Networks have proved to be useful representations of complex systems. Within these networks, there are typically a number of subsystems defined by only a subset of nodes and edges. Detecting these structures often provides important information about the organization and functioning of the overall network. Here, progress towards quantifying medium- and large-scale structures within complex networks is reviewed.

A completely ordered universe is as unexciting as an entirely disordered one. Interesting ‘complex’ phenomena arise in a middle ground. This article reviews the tools that have been developed to quantify structural complexity and to automatically discover patterns hidden between order and chaos.

Is the brain on the edge of criticality? Understanding the inner workings of the brain is a task made difficult by the number of elements involved: a hundred billion neurons and a hundred trillion synapses. Viewing the brain in terms of collective dynamics is one approach now yielding some insight.

A protein’s shape is crucial for fulfilling its function within a cell. This Review discusses how molecular dynamics simulations have given us insight into the processes that turn a linear chain of amino acids into a unique three-dimensional protein.