Abstract
Physics The Hall effect occurs when a current running through a conductor is deflected by a perpendicular magnetic field, causing a transverse voltage to develop. In certain semiconductor structures where the motion of the charge carriers is confined to two dimensions, this Hall voltage is quantized. When the parameter of quantization (the so-called filling factor ν) is an integer, the effect can be easily explained through the formation of Landau levels. Fractional filling factors may also occur, requiring a more involved explanation in terms of non-interacting composite fermions. Α state with ν = 5/2 is yet more exotic as it eludes the composite fermion description and was predicted to exhibit a complicated kind of quantum statistics known as non-Abelian, making it especially interesting for quantum computing. However, one of the assumptions of that prediction was that the state was also spin-polarized. Stern et al. test that assumption by measuring the photoluminescence of a GaAs-AlGaAs quantum well and find that the state appears to be spin-unpolarized. Their conclusions agree with those extracted from Raman and tilted-field measurements, prompting further theoretical research into whether a spin-unpolarized state can still support a non-Abelian theory for quantum computing applications. Phys. Rev. Lett. 105 , 96801 (2010).
Highlights
Transgenerational genetic effects—in this context, genetic variation in one generation that affects the phenotype of an offspring that has not inherited the variant—have been invoked as a means by which non-Mendelian inheritance may account in part for the current difficulty in explaining the known heritability of traits or of complex disease risk on the basis of known genetic variants
Α state with ν = 5/2 is yet more exotic as it eludes the composite fermion description and was predicted to exhibit a complicated kind of quantum statistics known as non-Abelian, making it especially interesting for quantum computing
Stern et al test that assumption by measuring the photoluminescence of a GaAs-AlGaAs quantum well and find that the state appears to be spinunpolarized. Their conclusions agree with those extracted from Raman and tilted-field measurements, prompting further theoretical research into whether a spin-unpolarized state can still support a non-Abelian theory for quantum computing applications. — JS
Summary
500 million years ago, schizochroal trilobites roamed the oceans, guided by compound eyes with bifocal lenses. Of its six pairs of eyes, the E2 eyes are tubular and face directly forward. They contain two retinas that are positioned at unequal distances from the lens, with photoreceptors oriented either parallel or perpendicular to the light path. Using a microscope to observe images formed by isolated lenses, the authors measured optical performance and determined that two distinct and wellfocused images are produced on the proximal and distal retinas, indicating a true bifocal lens. Nelson et al constructed chromosome substitution strains (CSSs) of male mice by replacing the Y chromosome of a host strain with that from a donor They examined the genetically identical female offspring from pairings of host strain females with either host strain males or CSS males.
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