Research articles

Two independent experiments demonstrate that quantum entanglement that has been lost in decoherence processes can be recovered. For the first time such ‘entanglement distillation’ has been achieved for states of light that are entangled in continuous variables, which should help to increase the distance over which quantum information can be distributed.

Entanglement swapping—a protocol for entangling remote quantum systems without the requirement of direct interaction between them—has been implemented in a completely deterministic fashion, allowing to prepare well-defined entangled states on demand.

Evidence for metal–insulator transitions in dilute 2D electron gases has sparked controversy and debate. A new model suggests such behaviour could arise from strong correlations driven by non-local Coulomb interactions, providing an alternative view to that which considers disorder to be the over-riding influence.

Optical lattice clocks, in which trapped atoms serve as a frequency reference, are promising candidates for next-generation atomic clocks. Depending on whether bosons or fermions are loaded into the lattice, fundamentally different design principles apply, as has now been shown.

The tendency of small objects to stick together as they come into contact is a commonly observed phenomenon. Yet the interactions that govern this behaviour can be complex. A systematic study of the variation in the force between a particle and a solid surface as they are brought together finds many parallels with the characteristics of glassy and granular systems.

Electron microscopes are regularly used to resolve atoms in solid samples. It turns out that they can also be used to image atoms in a Bose–Einstein condensate—remarkably, without destroying the coherent properties of the condensate.

A systematic study of the propagation of ultrasound through a random network of aluminium beads provides the first demonstration of the Anderson localization of classical waves in a 3D system.

Warm dense matter is a complex and little-explored state that is characterized by temperatures usually associated with plasmas but at densities similar to solids. A combination of inelastic X-ray scattering and ab initio simulations enables insight into its structure and behaviour.

The precision of various interferometric measurements can be enhanced by using entangled states of light. Now an experiment demonstrates that all the metrological advantages of the famed Hong–Ou–Mandel quantum interferometer can be realized even with purely classical light.

It is already known that the theory of quantum entanglement shares some analogies with the laws of thermodynamics. Now a rigorous and general link between the two fields has been established.

An experiment that demonstrates efficient absorption of light by a single atom residing in free space should be helpful for designing interfaces for the transfer of quantum information from ‘flying’ qubits to stationary quantum systems, without the need for optical cavities.

The computational capability of the brain remains a mystery. Some insight might come from a series of experiments in which cultures of living neurons are patterned in a way to form functional logic devices.

A key element in spintronics is the spin-transfer effect, by which the magnetization in a nanomagnet can be switched. The effect has already been demonstrated using spin-polarized electrical currents, but now reversible magnetization switching has been achieved using a pure, chargeless spin current.

An array of 488 Josephson junctions that amplifies and squeezes noise beyond conventional quantum limits should prove useful in the study and development of superconducting qubits and other quantum devices.

Application of extreme magnetic fields to a low-disorder 2D electron gas causes its electrons to reorder through an unexpected transition from a 2D to quasi-3D Wigner crystal state.

Coupling of the Rydberg states of an ensemble of rubidium atoms gives rise to a d.c. Kerr effect that is six orders of magnitude greater than in conventional Kerr media. Such phenomena could enable the development of high-precision electric field sensors and other nonlinear optical devices.

Separating two ferromagnetic layers with an appropriately chosen spacing layer enables the transfer of spin between the two, which increases the speed and degree of demagnetization induced by a laser pulse.

A technique that combines ideas taken from conventional scanning near-field optical microscopy and medical tomography enables structures within an anisotropic fluid to be imaged in 3D with sub-wavelength resolution.

Localized magnetic moments on surfaces can be screened through the Kondo effect by forming a correlated system with the surrounding conduction electrons. Measurements now show that the orientation of the magnetic moment’s spin relative to the surface has a decisive role in the physics of Kondo screening.

Analysis of the optical characteristics of a chip-based photonic crystal cavity embedded with a quantum dot demonstrates the occurrence of both photon tunnelling and photon blockade phenomena. Such behaviour could prove useful in the development of single-photon transistors and detectors.