Press releases
Please quote Nature Physics as the source of these items.
The March 2008 issue of Nature Physics is available online.
March 2008
Inside view of magnetic fields
A technique for three-dimensional visualization of magnetic fields inside bulk objects is reported online this week in Nature Physics. The method could provide insights into a wide range of problems in science and technology that involve magnetic phenomena in solid objects, including superconductivity and magnetic devices.
Nikolay Kardjilov and colleagues use elementary particles known as neutrons which carry no electrical charge and can penetrate thick layers of matter. They also posses a magnetic moment, that is, they act like tiny compass needles. These combined properties mean that neutrons sense magnetic fields inside bulk objects as they move through them.
Three-dimensional neutron imaging and probing of magnetic fields with neutrons have been demonstrated before in separate experiments, but Kardjilov’s team have now found a way to bring these applications together, and use the information carried by the neutrons to reconstruct images that show the full three-dimensional distribution of magnetic fields inside solid objects.
Three-dimensional imaging of magnetic fields with polarized neutrons
Nikolay Kardjilov, Ingo Manke, Markus Strobl, André Hilger, Wolfgang Treimer, Michael Meissner, Thomas Krist & John Banhart
Published online: 30 March 2008 | doi 10.1038/nphys912
'Superdense' coding gets denser
The record for the most amount of information sent in a single photon has been broken, according to a paper published online this week in Nature Physics. The study reports the transmission, on average, of 1.63 bits of information per photon.
According to classical physics, a photon can transport only one bit of information, by encoding a message that is limited to two possible statements, for example, 0 and 1. But when quantum-mechanical effects are exploited, a photon can carry, in theory, a two-bit message, which can encode four different statements. This protocol is known as 'superdense coding'.
Practical implementations, however, have so far been limited in how much of this quantum advantage could actually be exploited. Julio Barreiro and colleagues now overcome inherent limitations of earlier approaches, and introduce a technique that, in an optimized setting, would enable to use the full strength of 'superdense' coding.
Beating the channel capacity limit for linear photonic superdense coding
Julio T. Barreiro, Tzu-Chieh Wei & Paul G. Kwiat
Published online: 23 March 2008 | doi 10.1038/nphys919
Rocks on film
The fast formation of ponds and terraces of limestone at geothermal hot springs can be used to understand the physics of the striking patterns that rocks create, suggests a study online in Nature Physics this week. This work may have even broader implications — unwanted limestone also precipitates in pipes, and similar patterns are formed by dams of leaves and other forest 'litter' following rainfall.
John Veysey and Nigel Goldenfeld collected photographs of the Mammoth Hotspring complex in Yellowstone National Park, USA, over two years. They compared the actual pond growths to a computer simulation that modelled the limestone precipitation in the presence of turbulent fluid flow — a mechanism different from that in most river basins, where deposition happens in regions of calmer flow. The simulated terraces agreed with data on both length-scales and timescales and the resulting patterns looked the same on all length-scales.
Watching rocks grow
John Veysey II & Nigel Goldenfeld
Published online: 16 March 2008 | doi 10.1038/nphys911