| 1. |
- Alaverdyan, Yury, 1976, et al.
(författare)
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Optical antennas based on coupled nanoholes in thin metal films
- 2007
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Ingår i: Nature Physics. - : Springer Science and Business Media LLC. - 1745-2481 .- 1745-2473. ; 3:12, s. 884-889
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Tidskriftsartikel (refereegranskat)abstract
- The ability to control optical effects at the nanoscale is a challenge that could be of great importance for a range of photonic applications. However, progress requires a deep understanding of the relationship between near-field and far-field properties of the individual elements of the nanostructure, as well as of the role of nano-optical interactions. Here, we show that the strong interaction between nanoholes in optically thin metal films can be used to readily tune their spectral response and visibility. Control of this interaction in short chains of nanoholes enables either amplification or almost total suppression of the scattered light. The phenomena are interpreted in terms of hole coupling mediated via antisymmetric surface plasmon polaritons, which makes the nanohole chains effectively behave as linear wire antennas.
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| 2. |
- Amselem, Elias, et al.
(författare)
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Experimental four-qubit bound entanglement
- 2009
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Ingår i: Nature Physics. - 1745-2473 .- 1745-2481. ; 5:10, s. 748-752
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Tidskriftsartikel (refereegranskat)abstract
- Entanglement is one of the most puzzling features of quantum theory and of great importance for the new field of quantum information. Being a peculiar form of entanglement, bound entanglement emerges in certain mixed quantum states. This form of entanglement is not distillable by local operators and classical communication. Bound-entangled states are different from both the free entangled (distillable) and separable states. Here we report on the first experimental demonstration of a four-qubit polarization bound-entangled state, the so-called Smolin state. We have fully characterized its entanglement properties. Moreover, we have realized unlocking of the entanglement protocol for this state. The special properties of the Smolin state constitute a useful quantum resource for new multiparty communication schemes.
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| 3. |
- Babaev, Egor, et al.
(författare)
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Violation of the London law and Onsager-Feynman quantization in multicomponent superconductors
- 2007
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Ingår i: Nature Physics. - : Springer Science and Business Media LLC. - 1745-2473 .- 1745-2481. ; 3:8, s. 530-533
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Tidskriftsartikel (refereegranskat)abstract
- Non-classical response to rotation is a hallmark of quantum ordered states such as superconductors and superfluids. The rotational responses of all currently known single-component 'super' states of matter (superconductors, superfluids and supersolids) are largely described by two fundamental principles and fall into two categories according to whether the systems are composed of charged or neutral particles: the London law relating the angular velocity to a subsequently established magnetic field and the Onsager-Feynman quantization of superfluid velocity. These laws are theoretically shown to be violated in a two-component superconductor such as the projected liquid metallic states of hydrogen and deuterium at high pressures. The rotational responses of liquid metallic hydrogen or deuterium identify them as a new class of dissipationless states; they also directly point to a particular experimental route for verification of their existence.
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| 4. |
- Chapman, Henry N., et al.
(författare)
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Femtosecond diffractive imaging with a soft-X-ray free-electron laser
- 2006
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Ingår i: Nature Physics. - : Springer Science and Business Media LLC. - 1745-2473 .- 1745-2481. ; 2:12, s. 839-843
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Tidskriftsartikel (refereegranskat)abstract
- Theory predicts(1-4) that, with an ultrashort and extremely bright coherent X-ray pulse, a single diffraction pattern may be recorded from a large macromolecule, a virus or a cell before the sample explodes and turns into a plasma. Here we report the first experimental demonstration of this principle using the FLASH soft-X-ray free-electron laser. An intense 25 fs, 4 x 10(13) W cm(-2) pulse, containing 10(12) photons at 32 nm wavelength, produced a coherent diffraction pattern from a nanostructured non-periodic object, before destroying it at 60,000 K. A novel X-ray camera assured single-photon detection sensitivity by filtering out parasitic scattering and plasma radiation. The reconstructed image, obtained directly from the coherent pattern by phase retrieval through oversampling(5-9), shows no measurable damage, and is reconstructed at the diffraction-limited resolution. A three-dimensional data set may be assembled from such images when copies of a reproducible sample are exposed to the beam one by one(10).
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| 5. |
- Chen, Li-Jen, et al.
(författare)
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Observation of energetic electrons within magnetic islands
- 2008
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Ingår i: Nature Physics. - : Nature Publishing Group. - 1745-2473 .- 1745-2481. ; 4:1, s. 19-23
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic reconnection is the underlying process that releases impulsively an enormous amount of magnetic energy(1) in solar flares(2,3), flares on strongly magnetized neutron stars(4) and substorms in the Earth's magnetosphere(5). Studies of energy release during solar flares, in particular, indicate that up to 50% of the released energy is carried by accelerated 20-100 keV suprathermal electrons(6-8). How so many electrons can gain so much energy during reconnection has been a long-standing question. A recent theoretical study suggests that volume-filling contracting magnetic islands formed during reconnection can produce a large number of energetic electrons(9). Here we report the first evidence of the link between energetic electrons and magnetic islands during reconnection in the Earth's magnetosphere. The results indicate that energetic electron fluxes peak at sites of compressed density within islands, which imposes a new constraint on theories of electron acceleration.
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| 6. |
- Delsing, Per, 1959
(författare)
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Electrons go surfing one by one
- 2007
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Ingår i: Nature Physics. - : Springer Science and Business Media LLC. - 1745-2481 .- 1745-2473. ; 3:5, s. 300-301
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Although it is over 100 years since Millikan showed that electric charge is quantized, it is only with the development of a new generation of charge pumps that this fact can be used to define the fundamental unit of electrical current, the ampere. ©2007 Nature Publishing Group.
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| 7. |
- Diehl, S., et al.
(författare)
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Quantum states and phases in driven open quantum systems with cold atoms
- 2008
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Ingår i: Nature Physics. - : Nature Publishing Group. - 1745-2473 .- 1745-2481. ; 4:11, s. 878-883
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Tidskriftsartikel (refereegranskat)abstract
- An open quantum system, the time evolution of which is governed by a master equation, can be driven into a given pure quantum state by an appropriate design of the coupling between the system and the reservoir. This provides a route towards preparing many-body states and non-equilibrium quantum phases by quantum-reservoir engineering. Here, we discuss the example of a driven dissipative Bose–Einstein condensate of bosons and of paired fermions, where atoms in an optical lattice are coupled to a bath of Bogoliubov excitations and the atomic current represents local dissipation. In the absence of interactions, the lattice gas is driven into a pure state with long-range order. Weak interactions lead to a weakly mixed state, which in three dimensions can be understood as a depletion of the condensate, and in one and two dimensions exhibits properties reminiscent of a Luttinger liquid or a Kosterlitz–Thouless critical phase at finite temperature, with the role of the ’finite temperature’ taken by the interactions.
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| 8. |
- Kochukhov, Oleg, et al.
(författare)
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Weather in stellar atmosphere revealed by the dynamics of mercury clouds in alpha Andromedae
- 2007
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Ingår i: Nature Physics. - : Springer Science and Business Media LLC. - 1745-2473 .- 1745-2481. ; 3:8, s. 526-529
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Tidskriftsartikel (refereegranskat)abstract
- The formation of long-lasting structures at the surfaces of stars is commonly ascribed to the action of strong magnetic fields. This paradigm is supported by observations of evolving cool spots in the Sun and active late-type stars, and stationary chemical spots in the early-type magnetic stars. However, results of our seven-year monitoring of mercury spots in non-magnetic early-type star αAndromedae show that the picture of magnetically driven structure formation is fundamentally incomplete. Using an indirect stellar-surface mapping technique, we construct a series of two-dimensional images of starspots and discover a secular evolution of the mercury cloud cover in this star. This remarkable structure-formation process, observed for the first time in any star, is plausibly attributed to a non-equilibrium, dynamical evolution of the heavy-element clouds created by atomic diffusion, and may have the same underlying physics as the weather patterns on terrestrial and giant planets.
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| 9. |
- Li, Gene-Wei, et al.
(författare)
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Effects of macromolecular crowding and DNA looping on gene regulation kinetics.
- 2009
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Ingår i: Nature Physics. - 1745-2473 .- 1745-2481. ; 5:4, s. 294-297
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Tidskriftsartikel (refereegranskat)abstract
- DNA-binding proteins control how genomes function. The theory of facilitated diffusion(1) explains how DNA-binding proteins can find targets apparently faster than the diffusion limit by using reduced dimensionality(2,3)-combining three-dimensional (3D) diffusion through cytoplasm with 1D sliding along DNA (refs 3-15). However, it does not include a description of macromolecular crowding on DNA as observed in living cells. Here, we show that such a physical constraint to sliding greatly reduces the search speed, in agreement with single-molecule measurements. Interestingly, the generalized theory also reveals significant insights into the design principles of biology. First, it places a hard constraint on the total number of DNA-binding proteins per cell. Remarkably, the number measured for Escherichia coli fits within the optimal range. Secondly, it defines a new role for DNA looping, a ubiquitous topological motif in genomes. DNA looping can speed up the search process by bypassing proteins that block the sliding track close to the target.
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| 10. |
- Liu, Allen, et al.
(författare)
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Membrane-induced bundling of actin filaments
- 2008
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Ingår i: Nature Physics. - : Springer Science and Business Media LLC. - 1745-2473 .- 1745-2481. ; 4:10, s. 789-793
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Tidskriftsartikel (refereegranskat)abstract
- Dynamic interplay between the plasma membrane and underlying cytoskeleton is essential for cellular shape change. Spatial organization of actin filaments, the growth of which generates membrane deformations during motility(1), phagocytosis(2), endocytosis(3) and cytokinesis(4), is mediated by specific protein-protein interactions that branch, crosslink and bundle filaments into networks that interact with the membrane. Although membrane curvature has been found to influence binding of proteins with curvature-sensitive domains(5), the direct e effect of membrane elasticity on cytoskeletal network organization is not clear. Here, we show through in vitro reconstitution and elastic modelling that a lipid bilayer can drive the emergence of bundled actin filament protrusions from branched actin filament networks, thus playing a role normally attributed to actin-binding proteins. Formation of these filopodium-like protrusions with only a minimal set of purified proteins points to an active participation of the membrane in organizing actin filaments at the plasma membrane. In this way, elastic interactions between the membrane and cytoskeleton can cooperate with accessory proteins to drive cellular shape change.
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