HIGHLIGHTS

to maintain the polarization of the researchers’ proposal that lighter atoms Transformation during the excitation–emission process vibrate at higher therefore demonstrates the possibility of efficiently allowing a faster dissipation. transferring the information between a transmitting qubit (the photon) and the storage qubit (the electron spin), which is one of the essential requirements of quantum Soft moiré patterns information applications. Nano. Lett. doi:10.1021/nl071844k (2007) A moiré pattern is an interference pattern created when two lattices overlap with one Beneficial weight gain another. These patterns, commonly seen on television screens when someone is 2007 osa 2007 318, 780–783 (2007) © © wearing clothes of a particular weave, can Friction arises when two interfaces slide be used for studying microscopic strain in Opt. Express 15, 14772–14782 (2007) on each other and part of the kinetic materials. Recently moiré fringes have also The discovery of perfect imaging by energy converts into lattice vibrations and been shown to be a powerful tool for the materials with a negative transforms into heat. The microscopical generation of micro- and nanoscale patterns has opened a new field where artificial origin of friction is likely to depend on the and two-dimensional superlattices. Now enable an entirely new way chemical details of the surfaces. However, Manfred Stamm and colleagues observe of controlling the propagation of . Rachel Cannara and co-authors have now the rotation of moiré patterns produced by The powerful capabilities enabled by shown that the friction force can also be overlapping block-copolymer thin films metamaterials have recently been formalized tuned by modifying the mass of the atoms self-assembled in a well-defined hexagonal into a that describes how the electro- on an interface while leaving the chemistry morphology. These periodic superstructures optical parameters of metamaterials can be unchanged. They examined the sliding of appear when films with long-range order used to renormalize space and thus enable the tip of an atomic force microscope on the characteristics are superimposed at arbitrary control of the propagation of light surface of a diamond crystal and a silicon small misorientation angles. Disordered through space. One well-known application substrate terminated by either hydrogen nanoporous films can generate labyrinth-like of this ‘transformation optics’ is cloaking. To or deuterium. In all cases the friction is patterns and overlapping films misoriented further highlight the power of this approach, considerably greater for hydrogen. Although by 30° angles can produce aperiodic Schurig, Pendry and Smith present a number quantitatively the values of the friction quasi-crystal-like structures with five-fold of more practical optical elements. One force might be influenced by factors not symmetry. The authors suggest that these example is a perfect magnifying lens free considered in the present study — such block-copolymer superstructures could from geometric aberrations and with almost as the effect of surface defects — the prove useful as nanolithography masks with no back reflections. Although the planar data confirm quite unambiguously the controllable periodicity and morphology. structure of this lens and other possible devices eases their fabrication, advanced lithography will be required to fabricate such Unbreakable codes complex metamaterials with the necessary precision for practical frequencies in the Adv. Mater. 19, 3854–3858 (2007) optical range. Nevertheless, transformation One way to combat counterfeit optics may play a crucial role in complex pharmaceuticals is to label the drug itself integrated optics on a single chip. rather than the packaging. To achieve this, the encoded additive must be non-toxic, capable of storing an almost A selective memory unlimited number of codes and, bearing in mind drugs are usually administered New J. Phys. 9, 365 (2007) in tablet form, must survive compression The electronic states of semiconductor of the formulated drug during tablet quantum dots have already shown potential manufacture. Now, Stefaan De Smedt for quantum information. Robert Young and and colleagues show that by entrapping colleagues have now shown that a quantum digitally encoded microparticles dot can efficiently store the information (pictured) in starch-based granules, these contained in the polarization of a single high compression forces can be withstood 2007 WILEY 2007 photon. They embedded InAs quantum dots and the codes remain readable. If the © in a GaAs/AlAs diode, designed to allow the starch-based agglomerate is not formed detection of single . The researchers before compression, the microparticles by dissolution and filtration, they are used single photons with well-defined deform and are rendered unreadable. The decoded using fluorescence microscopy. polarization to optically inject electrons particles, which are composed partly from A weak is applied to ensure with specific spin. They then triggered polystyrene with immobilized fluorescent the correct orientation of the particles. the optical recombination of the electrons dye molecules and a ferromagnetic Initial cell-based studies show that the with holes injected by applying an alternate component, are encoded by bleaching microparticles are non-toxic — though to the diode after a desired delay. certain regions using confocal laser further toxicological tests are required, For delays as high as 1 μs the polarization microscopy. Following removal of this is a vital step towards the practical of the emitted photon was maintained the encoded particles from the drug, application of these encoded entities. with 80% efficiency. The ability of the dot | VOL 6 | DECEMBER 2007 | www.nature.com/naturematerials 919 © 2007 Nature Publishing Group