Reviews & Analysis

Photons emitted by extragalactic sources provide an opportunity to test quantum gravity effects that modify the speed of light in vacuum. Studying the arrival times of these cosmic messengers further constrains the energy scales involved.

The photons that make up visible light are indivisible. But certain organic materials can use singlet fission to divide the energy from one photon equally between two molecules. Experiments now reveal the molecular dynamics behind this phenomenon.

Over the past decade, ultracold polar molecules have found application in hybrid quantum computation and quantum simulation, directions established in three early papers published in Nature Physics.

Electrons moving in a one-dimensional crystal can acquire a geometrical phase. Sound waves in phononic crystals are now shown to display the same effect — underlining the similarity between conventional solids and acoustic metamaterials.

The transfer of protons across a high barrier only occasionally occurs through quantum-mechanical tunnelling. Low-temperature scanning tunnelling microscopy shows concerted tunnelling of four protons within chiral cyclic water tetramers supported on an inert surface.

Selective evaporation of one component from a mixture is a common process, but in the case of ultracold atomic gases, distillation is more complex.

The Rosetta orbiter following Comet 67P has captured not only the public imagination but also actual dust grains from the comet's nucleus, revealing their composition, morphology and strength.

The monopole picture for spin ice offers a natural description of a confounding class of materials. A 2009 paper in Nature Physics applied it to study the dynamical properties of these systems — sparking intense experimental and theoretical efforts in the years that followed.

Fluctuation theorems go beyond the linear response regime to describe systems far from equilibrium. But what happens to these theorems when we enter the quantum realm? The answers, it seems, are now coming thick and fast.

Experiments probing non-equilibrium processes have so far been tailored largely to classical systems. The endeavour to extend our understanding into the quantum realm is finding traction in studies of electronic circuits at sub-kelvin temperatures.

Equilibrium physics is ill-equipped to explain all of life’s subtleties, largely because living systems are out of equilibrium. Attempts to overcome this problem have given rise to a lively field of research—and some surprising biological findings.

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.

Photonic crystals can control the flow of light but they are extremely sensitive to structural disorder. Although this often degrades performance, disorder can actually be used to enhance light collimation.

Photons immediately spring to mind when we talk about long-distance entanglement. But the spins at the ends of one-dimensional magnetic chains can be entangled over large distances too — providing a solid-state alternative for quantum communication protocols.

The valley index of an electron is a magnetic moment that can be initialized optically and probed electrically. Now, experiments reveal how magnetic fields can break the degeneracy for states with different valley indices.

The Higgs mechanism is normally associated with high energy physics, but its roots lie in superconductivity. And now there is evidence for a Higgs mode in disordered superconductors near the superconductor–insulator transition.

Even simple periodic mechanical lattices can exhibit exotic topologically protected modes. Incorporating defects into the mix makes things more interesting — revealing modes whose characteristics depend on properties of both the lattice and the defect.

The successful formation of self-generated magnetic fields in the lab using large-scale, high-power lasers opens the door to a better understanding of some of the most extreme astrophysical processes taking place in the Universe.