Articles in 2010

The processors of most computers work in series, performing one instruction at a time. This limits their ability to perform certain types of tasks in a reasonable period. An approach based on arrays of simultaneously interacting molecular switches could enable previously intractable computational problems to be solved.

Recently, coherent quantum beating has been observed in photosynthetic complexes. Theoretical work now shows how quantum correlations in biological systems can be quantified, and establishes that quantum entanglement exists in light-harvesting complexes, even at physiological temperatures.

The high-order harmonics of short laser pulses created in a nonlinear medium are a useful source of extreme-ultraviolet and soft-X-ray radiation. A newly discovered phenomenon that amplifies this emission even further could improve the efficiency of short-wavelength light sources.

Macrorealism assumes that a macroscopic object is at any given time in one of the distinct states it has available, and that it is in principle possible to determine which state the system is in without disturbing its dynamics. An experiment now demonstrates that a superconducting microelectronic system violates macrorealism and obeys the laws of quantum mechanics.

Granular flows, such as in silos or desert sandstorms, can form charged particle clouds in the presence of an electric field. Simulations and experiments on inert grains explain how significant electrical charges are able to accumulate.

When a superconductor is in contact with a normal metal, Cooper pairs from the superconductor ‘leak’ into the metal, causing local superconductivity. When in contact with a ferromagnet, however, Cooper pairs do not stray very far. Therefore, the discovery that a ferromagnetic nanowire goes completely superconducting when placed between two superconducting electrodes is surprising indeed.

Mott insulators are driven by strong Coulomb repulsion and topological insulators by strong spin–orbit coupling. Although these effects are normally in competition, in some cases the Coulomb interaction can enhance the effects of spin–orbit coupling. Together these interactions could lead to gapless spin-only excitations on the surface of a strongly correlated insulator.

From observations we know that stem-cell development depends on the elastic properties of the surface on which the cells are found or the matrix in which the cells are placed. A study combining both theory and experiment now provides a physical model for the part played by substrate elasticity in cell differentiation and function.

Building on recent experimental advances in controlling individual Rydberg atoms, theoretical work proposes a ‘Rydberg quantum simulator’. Such a system would be suitable for efficiently simulating other quantum systems with many-body interactions and strongly correlated ground states.

Axions are hypothetical particles that might play an important part in particle physics, astrophysics and cosmology. So far they have eluded observation, but theoretical work now predicts that axion physics might be explored in condensed-matter systems known as topological insulators.

Modelling the interaction of an intense laser with a plasma in an optimal ‘Lorentz boosted’ frame of reference decreases by many orders of magnitude the computation time needed to simulate a laser-driven particle accelerator. This provides a powerful tool for optimizing the characteristics of accelerators driven by the next generation of high-intensity lasers, which will be able to deliver powers beyond a petawatt.

Building on ideas from quantum information science and on recent experimental advances, the use of ultracold alkaline-earth atoms in optical lattices as quantum simulators of many-body phenomena is proposed. The corresponding models possess a high degree of symmetry and may provide fundamental insights into strongly correlated systems.

The minimum noise energy that a phase-preserving amplifier adds to the signal is fundamentally limited to half a photon. A proposed parametric amplifier based on Josephson junctions should be able to reach this limit at microwave frequencies.

A microfluidic valve that amplifies the pressure in a fluid channel enables the realization of static microfluidic digital control logic. This in turn could enable more versatility and integration in the control of flows in ‘lab-on-a-chip’ systems.

Turbulence usually makes plasmas more homogeneous. But in an unusual device for which the confining field is generated by a levitated half-tonne superconducting magnet, a study finds that turbulent fluctuations can actually increase the density of a plasma by driving diffusion against a density gradient.

Advances in X-ray imaging are allowing the investigation of molecular dynamics on an attosecond timescale and at angstrom-scale spatial resolution. It is now even possible to reconstruct images of the molecular orbitals, which provides us with a better understanding of how molecules respond to intense fields.

Although ‘random lasing’ in disordered optical media was first demonstrated a decade ago, the mechanism by which it occurs is disputed. New evidence of random lasing in conjugated polymers strongly supports the notion that it is generated within random optical cavities that naturally occur within disordered media.

Mimicking even the simplest of animal behaviour, such as walking along uneven terrain, is a challenging task. A study finds that incorporating a simple but inherently chaotic pattern generator into the control system of an autonomous robot allows it to show adaptive behaviour, enabling it to successfully navigate through a complex environment.