Volume 7 Issue 5, May 2011

An 'attoclock' that measures the relative release time of electrons during double ionization may force us to rethink our use of semi-classical models.

Intense femtosecond pulses of infrared light can manipulate molecules. It is now shown that such control even extends to making different molecular eigenstates interfere with each other in a way never considered before — a potential tool for optically engineered chemical reactions and for ultrafast information encoding and manipulation.

The observation of quantum phenomena usually requires utmost control and isolation of a quantum system from its noisy environment. A study now shows how even a spontaneously emitted photon may force an atom into a coherent quantum state.

Elegant but extremely delicate quantum procedures can increase the precision of measurements. Characterizing how they cope with the detrimental effects of noise is essential for deployment to the real world.

A century ago, Heike Kamerlingh Onnes discovered superconductivity. And yet, despite the conventional superconductors being understood, the list of unconventional superconductors is growing — for which unconventional theories may be required.

An atom recoils as it emits a photon. Researchers now show that the two possible recoil trajectories become coherently superimposed when a mirror is placed near the atom. This is because the mirror prevents the photon from giving away any information about the recoil direction.

Intense femtosecond pulses of infrared light are frequently used to manipulate molecules. It is now shown that such control even extends to making different molecular eigenstates interfere with each other — an effect that could potentially pave the way to using molecules for quantum information processing.

Gate-tunable Andreev bound states that arise within quantum dots formed beneath superconducting contacts deposited on a graphene sheet could be useful in the development of solid-state qubits.

Coating a spherical colloid with a nematic liquid crystal causes frustration-induced defects in the crystal. The thickness of this coating can be used to systematically control the number and orientation of these defects, which could be useful for engineering the microstructure of colloidal materials.

A liquid droplet placed on a hot surface can levitate, and moreover, self-propel if the surface is textured. Solids can similarly self-propel, which means that the properties of the liquid are irrelevant. Rather, it is the vapour beneath the drop that does the propelling.

Quantum simulations, where one quantum system is used to emulate another, are starting to become experimentally feasible. Here, four-photon states are used to simulate spin tetramers, which are important in the description of certain solid-state systems. Emerging frustration within the tetramer is observed, as well as evolution of the ground state from a localized to a resonating-valence-bond state.

Quantum strategies can help to make parameter-estimation schemes more precise, but for noisy processes it is typically not known how large that improvement may be. Here, a universal quantum bound is derived for the error in the estimation of parameters that characterize dynamical processes.

Topological quantum computation schemes — where quantum information is stored non-locally — provide, in theory, an elegant way of avoiding the deleterious effects of decoherence, but they have proved difficult to realize experimentally. A proposal to engineer topological phases into networks of one-dimensional semiconducting wires should bring topological quantum computers a step closer.

Most of the notable properties of graphene are a result of the cone-like nature of the points in its electronic structure where its conduction and valance bands meet. Similar structures arise in 2D HgTe quantum wells, but without the spin- and valley-degeneracy of graphene; their properties are also likely to be easier to control.

The atom-like electronic structure of semiconductor quantum dots makes them ideal for storing well-defined numbers of electrons. This in turn can be used in the development of standards for current, to independently define the ampere.

An ‘attoclock’ that measures the relative release time of electrons during double ionization is now presented. The technique enables investigation of the subtle differences between sequential and non-sequential ionization when elliptically polarized light is used to excite two electrons from argon atoms.

Ultracold quantum gases in optical lattices have been used to study a wide range of many-body effects. Nearly all experiments so far, however, have been performed in cubic optical lattice structures. Now a ‘honeycomb’ lattice structure has been realized. The approach promises insight into materials with hexagonal crystal symmetries, such as graphene or carbon nanotubes.