Letters in 2008

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.

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.

When current is passed through certain semiconductors or metals, spins of opposite sign accumulate on opposing boundaries. The phenomenon is known as the spin Hall effect, and now, for the first time, its dynamics has been measured directly.

Maxwell’s equations describing electric and magnetic fields limit the shapes field lines can take. But exotic solutions exist where the field lines are linked and knotted. A proposal now shows how such solutions could be realized experimentally.

Superconducting quantum interference devices, or SQUIDs as they are better known, are capable of detecting minute variations in magnetic field. Embedding a suspended beam into the structure of d.c. SQUID enables this sensitivity to be exploited for measuring displacements.

Cells can change shape by reorganizing the actin filaments that make up the cytoskeleton, and this is usually achieved through protein interactions. But it seems that the cell membrane, by virtue of its elasticity, can also influence the bundling of actin filaments.

Coherent population trapping is a process by which a particle is induced to exist in a superposition of two ground states. This has now been demonstrated for an electron spin on a single quantum dot, which could prove useful in a variety of photonic and information-processing applications.

The integration of a micrometre-sized magnet with a semiconductor device has enabled the individual manipulation of two single electron spins. This approach may provide a scalable route for quantum computing with electron spins confined in quantum dots.

That the dynamical properties of a glass-forming liquid at high temperature are different from behaviour in the supercooled state has already been established. Numerical simulations now suggest that the static length scale over which spatial correlations exist also changes on approaching the glass transition.

A technique that controls electron spins using single optical pulses far detuned from the optical transition has been demonstrated. This approach may enable fast spin manipulation in a variety of solid-state systems.

When a superfluid—such as liquid helium—is set in rotation, vortices appear in which circulation around a closed loop can take only discrete values. Such quantized vortices have now been observed in a solid-state system—a Bose–Einstein condensate made of exciton polaritons.

The observation of so-called Bogoliubov excitations provides the first sign of possible superfluid behaviour in an exciton-polariton condensate.

Detailed analysis of multiscale structures and the identification of long-lived streamer-like wavemodes in a magnetically confined plasma provides new insight into the physics of plasma turbulence.

Disorder and geometric frustration usually lead to magnetic spins that point in random directions, as in a spin glass. So how can spin-glass behaviour emerge in a well-ordered system without static frustration? The presence of ‘dynamic frustration’ may explain the situation.

The observation of controlled adiabatic evolution from paramagnetic into ferromagnetic order in a system made of two trapped ions represents an initial step into the emerging field of quantum simulation.

A simulation establishes the relationship between structural relaxation in a supercooled liquid and the low-frequency dynamics in the underlying inherent structures.