Reviews & Analysis

The tracking of the circulation of dollar bills around the United States, to map human travel patterns, has at last uncovered a physical example of a particular style of random walk.

Certain aspects of two-dimensional turbulence are remarkably similar to those found in critical percolation, and show conformal invariance. But there is both less, and more, to this observation than meets the eye.

The coalescence of neutron stars in compact binaries could produce the intense, short flashes of high-energy radiation observed in gamma-ray bursts. Models suggest that dynamical evolution in old dense stellar clusters, rather than galaxies, may form many of these rare systems.

Treating cancer with beams of high-energy protons is just one of the exciting possibilities presented by the advent of laser-based particle accelerators. But how soon will these devices reach the performance levels needed for such applications, and how will these improvements be made?

Depending on the temperature, the flow of current between two reservoirs of superfluid ⁴He exhibits phase slippage — a mechanism that creates vortices and leads to energy dissipation — or Josephson oscillations when the apertures connecting the reservoirs behave as a weak link.

The role of phonons in conventional superconductivity — first determined by isotope substitution — has been known for over half a century. But identifying the mechanism in unconventional superconductivity is a much more challenging affair.

The observation of macroscopic quantum coherent behaviour by a single polymer chain provides an important model system for studying the physics of reduced dimensionality, unperturbed by the disorder that can complicate the study of conventional inorganic systems.

The melting temperatures of the base-pair sequences in DNA are difficult to predict. But applying statistical physics to the problem has created an 'index' that well represents the molecule's thermal properties.

The ability to measure small or slow rotations relative to an inertial frame is valuable in navigation as well as in fundamental physics. A device that exploits techniques developed in atomic physics could lead to sensitive and compact rotation sensors.

For a 'real life' quantum computer, mere capability is not good enough. It also has to defy disturbances attempting to weaken its special powers. To succeed, the task has to be addressed on various levels.

Repetition is probably the simplest method of error control. If an experiment fails, repeat it, and do so until it eventually succeeds. Quantum mechanics gives leeway for alternative approaches.

A tighter limit on the half-life of a tellurium nucleus for 'neutrinoless double-beta decay' marks progress towards a better understanding of the ever-elusive neutrinos and the measurement of their mass.

The emergence of both complex and repeating patterns in a simple microfluidic circuit provides an ideal test-bed for studying self-organized complexity, without the need for exhaustive dynamic control over the parameters that influence complex behaviour.

Computer viruses can spread through networks with alarming speed. But there is hope that those fighting the plague can keep up with the pace.

Berry phases and hidden chiralities are thought to be behind some of the most exotic states in quantum magnets. Polarized neutron scattering unveils the influence of such behaviour on the dynamics of quantum systems.

A planet's rings can be distorted by the gravitational pull of its satellites, and these complex interactions have been difficult to disentangle. Saturn's moon Prometheus, however, has now been caught returning to the scene of the crime.

The spin of a photoluminescent nitrogen centre in diamond has a long life-time that could be useful as a qubit, for example. It's difficult enough to image such a single spin — imagine using that bright spin to detect nearby invisible 'dark' spins.

An atomic Bose–Einstein condensate represents a highly correlated, coherent state of matter. Experiments now reveal that the collective matter-wave properties extend to include coherent dynamics of the spin degrees of freedom.