May 2011 Volume 7, Issue 5

Editorial

Nuclear power for the next generation p367
doi:10.1038/nphys2003
The situation at Japan's Fukushima Dai-ichi nuclear power plant is dire, but should not turn the world off nuclear power.
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Thesis

A climate for discussion p369
Mark Buchanan
doi:10.1038/nphys1995
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Research Highlights

Our choice from the recent literature p370
doi:10.1038/nphys2001
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News and Views

Letters

Single spontaneous photon as a coherent beamsplitter for an atomic matter-wave pp379 - 382
Jiri Tomkovič, Michael Schreiber, Joachim Welte, Martin Kiffner, Jörg Schmiedmayer and Markus K. Oberthaler
doi:10.1038/nphys1961
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.
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See also: News and Views by Arndt

Strong-laser-induced quantum interference pp383 - 385
Haruka Goto, Hiroyuki Katsuki, Heide Ibrahim, Hisashi Chiba and Kenji Ohmori
doi:10.1038/nphys1960
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.
First paragraph | Full Text | PDF
See also: News and Views by Baumert

Transport through Andreev bound states in a graphene quantum dot pp386 - 390
Travis Dirks, Taylor L. Hughes, Siddhartha Lal, Bruno Uchoa, Yung-Fu Chen, Cesar Chialvo, Paul M. Goldbart and Nadya Mason
doi:10.1038/nphys1911
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.
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Frustrated nematic order in spherical geometries pp391 - 394
T. Lopez-Leon, V. Koning, K. B. S. Devaiah, V. Vitelli and A. Fernandez-Nieves
doi:10.1038/nphys1920
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.
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Leidenfrost on a ratchet pp395 - 398
Guillaume Lagubeau, Marie Le Merrer, Christophe Clanet and David Quéré
doi:10.1038/nphys1925
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.
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Articles

Quantum simulation of the wavefunction to probe frustrated Heisenberg spin systems pp399 - 405
Xiao-song Ma, Borivoje Dakic, William Naylor, Anton Zeilinger and Philip Walther
doi:10.1038/nphys1919
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.
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General framework for estimating the ultimate precision limit in noisy quantum-enhanced metrology pp406 - 411
B. M. Escher, R. L. de Matos Filho and L. Davidovich
doi:10.1038/nphys1958
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.
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See also: News and Views by Maccone & Giovannetti

Non-Abelian statistics and topological quantum information processing in 1D wire networks pp412 - 417
Jason Alicea, Yuval Oreg, Gil Refael, Felix von Oppen and Matthew P. A. Fisher
doi:10.1038/nphys1915
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.
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Single valley Dirac fermions in zero-gap HgTe quantum wells pp418 - 422
B. Büttner, C. X. Liu, G. Tkachov, E. G. Novik, C. Brüne, H. Buhmann, E. M. Hankiewicz, P. Recher, B. Trauzettel, S. C. Zhang and L. W. Molenkamp
doi:10.1038/nphys1914
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.
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Current quantization in an optically driven electron pump based on self-assembled quantum dots pp423 - 427
L. Nevou, V. Liverini, P. Friedli, F. Castellano, A. Bismuto, H. Sigg, F. Gramm, E. Muller and J. Faist
doi:10.1038/nphys1918
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.
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Timing the release in sequential double ionization pp428 - 433
Adrian N. Pfeiffer, Claudio Cirelli, Mathias Smolarski, Reinhard Dörner and Ursula Keller
doi:10.1038/nphys1946
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.
Abstract | Full Text | PDF
See also: News and Views by Ueda & Ishikawa

Multi-component quantum gases in spin-dependent hexagonal lattices pp434 - 440
P. Soltan-Panahi, J. Struck, P. Hauke, A. Bick, W. Plenkers, G. Meineke, C. Becker, P. Windpassinger, M. Lewenstein and K. Sengstock
doi:10.1038/nphys1916
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.
Abstract | Full Text | PDF