Volume 7 Issue 7, July 2011

Refined techniques to mix cold antiprotons and positrons in a magnetic bottle show that antihydrogen atoms can be trapped for 15 minutes — an improvement of four orders of magnitude over previous experiments.

The alignment of the nuclear spins in parahydrogen can be transferred to other molecules, where it enhances NMR signals by several orders of magnitude. This approach enables NMR even in the absence of magnetic fields, and offers unprecedented opportunities in physics, chemistry, biology and medicine.

Extensive numerical simulations provide evidence that the thermodynamic behaviour of supercooled silicon is similar to that proposed for supercooled water: a line of liquid–liquid transitions that ends at a critical point. In the case of silicon, however, the critical point occurs at negative pressures.

Noise filters based on so-called dynamical decoupling pulse sequences can suppress decoherence in quantum systems. Turning this idea on its head now provides a new technique for studying the noise itself.

Microscale resonators cooled so that their vibrational motion approaches the quantum limit enable the study of quantum effects in macroscopic systems. An approach that could probe the interface between quantum mechanics and general relativity is now demonstrated by using lasers to suspend a glass microsphere in a vacuum.

In electromagnetism, the vector potential generates magnetic fields through its spatial variation and electric fields through its time dependence. Now, it is demonstrated that, by engineering a time-varying vector potential acting on an atomic Bose–Einstein condensate, a synthetic gauge field can be generated that has the effect of an electric field on the atoms, even if these are neutral.

Although evidence indicates that defects induce magnetism in graphite, it’s unclear whether this extends to graphene. An observation of the gate-tunable Kondo effect in ion-beam-damaged graphene suggests it does.

Magnetic reconnection is important to the dynamics of many astrophysical and fusion plasmas but our understanding of it is incomplete. Petaflop-scale simulations of the evolution of turbulent magnetic reconnection in a three-dimensional plasma indicate that it proceeds in a way that is dramatically different from classical theory.

When a high-intensity laser pulse interacts with a plasma it generates immense fields that can accelerate charged particles. Combining high-speed polarimetry and plasma shadowgraph enables the detailed evolution of this process to be imaged in real time.

The full phase diagram of supercooled silicon has not been accessible experimentally, so the critical behaviour is highly debated. Numerical simulations now reveal a liquid–liquid critical end-point at negative pressure. This study further supports the similarity between silicon and water.

An analytic model now provides quantitative predictions for the effect of void fractions within a granular medium on avalanche statistics. It will help us understand the dynamics of earthquakes as well as plasticity.

Antihydrogen has been created, trapped and stored for 1,000 s. The improved holding time means that we now have access to the ground state of antimatter—long enough to test whether matter and antimatter obey the same physical laws.

A technique to study the noise in quantum systems has been devised by using spectral filters in reverse. So-called dynamical-decoupling pulse sequences, previously used to remove noise, now quantify how a superconducting qubit interacts with its noisy environment.

NMR is typically carried out in strong magnetic fields, but recent technological developments have enabled the development of different methods for creating and detecting nuclear magnetization that do not depend on the use of strong magnets. A study that combines such methods demonstrates now that high-resolution NMR spectra with chemically relevant information can be obtained at zero magnetic field.

That Brownian particles in a liquid move diffusively at long times but ballistically at very short times has been understood for more than a century. However, the full details of the transition between these regimes are yet to be explored. Now, the transition from ballistic to diffusive Brownian motion has been measured for the first time.

Extensive datasets such as those capturing the movement of mobile-phone users have provided us with a new basis for modelling human mobility, a process that has been shown to be highly predictable. This study now shows how recurrent patterns in how we move influence contagion processes, such as the spatial spread of infectious diseases.