Volume 4 Issue 11, November 2008

Science once enjoyed a close and fruitful relationship with the White House and Capitol Hill — one that must now be rekindled, as a new president and Congress take office.

The 2008 Nobel Prize for physics has been awarded to Yoichiro Nambu “for the discovery of the mechanism of spontaneous broken symmetry in subatomic physics”, and to Makoto Kobayashi and Toshihide Maskawa “for the discovery of the origin of the broken symmetry which predicts the existence of at least three families of quarks in nature”.

Detailed investigation of a single atomic spin on a surface reveals that its Kondo interaction with the substrate electrons depends strongly on the spin's relative orientation.

The theory of quantum entanglement shares a number of analogies with the laws of thermodynamics, but still there are some differences. New results reveal a more complete thermodynamic structure behind entanglement.

A fresh take on perturbation theory allows quantum-mechanical interactions to be simplified, while preserving low-energy properties, and deepens understanding of the complexity of quantum systems.

Theories of the spin Hall effect suggest that spin currents generated by electric fields accumulate spin polarization at the sample edges. Now an experiment has observed this conversion in real time.

For nearly two decades physicists have been learning to incorporate spin into conventional electronics. Now they may be one step closer to devices that use only flow of spins, but not of charges.

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.

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.

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.

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.

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.

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.

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.

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.

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.

The coupling of a quantum system to its environment is usually associated with the unwanted effect of decoherence. But theoretical work shows that with suitably engineered couplings, dissipation can drive a system of cold atoms into desired many-body states and quantum phases.

Interactions between photons are typically extremely weak. But when light pulses are confined to an optical waveguide and manipulated with nearby cold atoms, strongly interacting photons can be created that may even undergo crystallization, as is now shown theoretically.

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.

Politics can be hard to swallow.