Table of contents

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Let battle commence p739


The final bids are in to host a major radio telescope, the Square Kilometre Array.



Drum roll p741

Mark Buchanan



Book Review

A new kind of science? p742

Reinventing Discovery: The New Era of Networked Science by Michael Nielsen



News and Views

One-dimensional metals: Luttingers wake pp744 - 745

Hanno Weitering


A strictly one-dimensional electron liquid or 'Luttinger liquid' may seem a purely theoretical construct. But measurements of the electronic structure of strings of gold atoms self-aligned on a germanium surface suggest this mythic state of matter is real, offering new possibilities to investigate and ultimately control its properties and behaviour.

Subject terms: Condensed-matter physics | Nanotechnology

See also: Letter by Blumenstein et al.

Scientific literature: Less room for failure p745

Andreas Trabesinger


Subject term: Other physics

Materials spectroscopy: What would Schrödinger's cat see? p746

Carlo Piermarocchi


Quantum states of light could be a better probe for materials than classical states, but they are hard to generate in the laboratory. A scheme that combines large amounts of data with sophisticated theoretical analysis gets around this limitation.

Subject terms: Quantum physics | Condensed-matter physics | Techniques and instrumentation

See also: Article by Kira et al.

Electron diffraction: Cool beams in great shape pp747 - 748

Edgar Vredenbregt & Jom Luiten


A demonstration of the ability to produce arbitrary-shaped electron bunches from an ultracold gas represents an important step towards studying ultrafast molecular processes in laboratories around the world.

Subject terms: Particle physics | Optical physics

See also: Letter by McCulloch et al.

Semiconductors: Electrons surf the wave p748

David Gevaux


Subject term: Electronics, photonics and device physics

Oxide interfaces: Moment of magnetism pp749 - 750

Andrew J. Millis


Electrons at an interface between two insulating oxides are now shown to exhibit ferromagnetism — a collective electronic state not seen in the bulk of either individual oxide.

Subject terms: Condensed-matter physics | Electronics, photonics and device physics

See also: Letter by Li et al. | Letter by Bert et al.

Glass physics: Prigogine and Defay say relax pp750 - 751

C. Austen Angell & Iolanda Santana Klein


For an important class of liquids, relaxation dynamics are constrained by a surprisingly simple scaling relationship between density and temperature. It seems that thermodynamics holds the key to pinning down the exponent.

Subject term: Statistical physics, thermodynamics and nonlinear dynamics

See also: Article by Gundermann et al.



Experimental investigation of the entanglement-assisted entropic uncertainty principle pp752 - 756

Chuan-Feng Li, Jin-Shi Xu, Xiao-Ye Xu, Ke Li & Guang-Can Guo


Heisenberg’s uncertainty principle limits the precision with which we can measure two complementary properties of a quantum system. Entanglement, it has previously been proposed, can relax these constraints. This idea is now demonstrated experimentally with the aid of polarization-entangled photons.

Subject terms: Quantum physics | Optical physics

See also: Letter by Prevedel et al.

Experimental investigation of the uncertainty principle in the presence of quantum memory and its application to witnessing entanglement pp757 - 761

Robert Prevedel, Deny R. Hamel, Roger Colbeck, Kent Fisher & Kevin J. Resch


The uncertainty principle tells us that two associated properties of a particle cannot be simultaneously known with infinite precision. However, if the particle is entangled with a quantum memory, the uncertainty of a measurement is reduced. This concept is now observed experimentally.

Subject terms: Quantum physics | Optical physics

See also: Letter by Li et al.

Coexistence of magnetic order and two-dimensional superconductivity at LaAlO3/SrTiO3 interfaces pp762 - 766

Lu Li, C. Richter, J. Mannhart & R. C. Ashoori


Lanthanum aluminate and strontium titanate are insulators, but when you bring them together, the interface between them becomes a two-dimensional superconductor. Even more surprising, magnetometry and transport measurements show that this superconducting state coexists with magnetic order.

Subject term: Condensed-matter physics

See also: News and Views by Millis | Letter by Bert et al.

Direct imaging of the coexistence of ferromagnetism and superconductivity at the LaAlO3/SrTiO3 interface pp767 - 771

Julie A. Bert, Beena Kalisky, Christopher Bell, Minu Kim, Yasuyuki Hikita, Harold Y. Hwang & Kathryn A. Moler


When the insulators lanthanum aluminate and strontium titanate are brought together, the interface between them forms a two-dimensional superconductor. Moreover, magnetic imaging of this interface shows that superconductivity and ferromagnetism coexist in separated nanoscale domains.

Subject term: Condensed-matter physics

See also: Letter by Li et al. | News and Views by Millis

Topological entanglement entropy of a Bose–Hubbard spin liquid pp772 - 775

Sergei V. Isakov, Matthew B. Hastings & Roger G. Melko


Spin liquids are states of matter that reside outside the regime where the Landau paradigm for classifying phases can be applied. This makes them interesting, but also hard to find, as no conventional order parameters exist. The authors demonstrate that topologically ordered spin-liquid phases can be identified by numerically evaluating a measure known as topological entanglement entropy.

Subject terms: Condensed-matter physics | Quantum physics

Atomically controlled quantum chains hosting a Tomonaga–Luttinger liquid pp776 - 780

C. Blumenstein, J. Schäfer, S. Mietke, S. Meyer, A. Dollinger, M. Lochner, X. Y. Cui, L. Patthey, R. Matzdorf & R. Claessen


The Tomonaga–Luttinger liquid model is the leading candidate for describing one-dimensional metallic conductors at low temperature. Yet, experimental evidence that it is valid is sketchy. Scanning tunnelling and photoemission spectra suggest that it does, in fact, describe the behaviour of chains of gold atoms self-assembled on the surface of germanium.

Subject terms: Condensed-matter physics | Nanotechnology

See also: News and Views by Weitering

Extreme-ultraviolet pump–probe studies of one-femtosecond-scale electron dynamics pp781 - 784

P. Tzallas, E. Skantzakis, L. A. A. Nikolopoulos, G. D. Tsakiris & D. Charalambidis


Pump–probe measurements are now an essential tool for investigating ultrafast dynamics in atoms and molecules. A lack of sources producing high-intensity attosecond pulses of extreme-ultraviolet (EUV) light has, however, hindered progress. Now, a technique that induces nonlinear processes with EUV light is demonstrated that could circumvent this problem.

Subject terms: Optical physics | Atomic and molecular physics

Arbitrarily shaped high-coherence electron bunches from cold atoms pp785 - 788

A. J. McCulloch, D. V. Sheludko, S. D. Saliba, S. C. Bell, M. Junker, K. A. Nugent & R. E. Scholten


The potential to generate pulsed electron beams with charge distributions tailored in all three dimensions could revolutionize high-speed electron diffraction. A demonstration of a highly coherent pulse electron beam that can be arbitrarily tailored in two dimensions is a step towards this goal.

Subject terms: Particle physics | Optical physics

See also: News and Views by Vredenbregt & Luiten



A quantum memory intrinsic to single nitrogen–vacancy centres in diamond pp789 - 793

G. D. Fuchs, G. Burkard, P. V. Klimov & D. D. Awschalom


A nitrogen impurity in diamond—where two of the carbon atoms are replaced by a nitrogen atom and a vacant lattice site—is seen as a valuable qubit. The spin of an electron localized to the nitrogen-vacancy centre is commonly used for processing. Researchers now show that this electron spin state can be transferred to the nitrogen nuclear spin, where it can be stored until needed.

Subject terms: Quantum physics | Electronics, photonics and device physics

Unconditional room-temperature quantum memory pp794 - 798

M. Hosseini, G. Campbell, B. M. Sparkes, P. K. Lam & B. C. Buchler


Optical quantum memories—storage devices for the data encoded in light pulses—will be vital for buffering the flow of quantum information. Researchers now demonstrate such a device that can operate at room temperature. The quantum state is stored in a vapour of rubidium atoms and then recalled with a fidelity in excess of 98%.

Subject terms: Quantum physics | Optical physics

Quantum spectroscopy with Schrödinger-cat states pp799 - 804

M. Kira, S. W. Koch, R. P. Smith, A. E. Hunter & S. T. Cundiff


Experiments that exploit non-classical properties of light promise to provide unique information about many-body systems. The limited availability of non-classical light sources, however, makes their implementation challenging. A method to calculate the quantum-optical response of a material from signals measured by using coherent-light excitation might provide an alternative route.

Subject terms: Quantum physics | Condensed-matter physics | Techniques and instrumentation

See also: News and Views by Piermarocchi

Nodal quasiparticle meltdown in ultrahigh-resolution pump–probe angle-resolved photoemission pp805 - 809

J. Graf, C. Jozwiak, C. L. Smallwood, H. Eisaki, R. A. Kaindl, D-H. Lee & A. Lanzara


Where a superconductor has a node, or a zero, in the superconducting gap, low-energy excitations exist that are similar to those in normal metals and are thought to be unaffected by superconductivity. However, excitation of superconductors with a near infrared pulse reveals there is a link between these excitations and superconductivity.

Subject terms: Condensed-matter physics | Materials physics

Aharonov–Bohm interferences from local deformations in graphene pp810 - 815

Fernando de Juan, Alberto Cortijo, María A. H. Vozmediano & Andrés Cano


Mechanical deformations in graphene have been shown to be associated with ‘fictitious’ magnetic fields. Theoretical work now suggests that these fields can give rise to an analogue of the Aharonov–Bohm effect, a phenomenon that might be used to sensitively detect small deformations of the graphene sheet.

Subject terms: Condensed-matter physics | Electronics, photonics and device physics | Nanotechnology

Predicting the density-scaling exponent of a glass-forming liquid from Prigogine–Defay ratio measurements pp816 - 821

Ditte Gundermann, Ulf R. Pedersen, Tina Hecksher, Nicholas P. Bailey, Bo Jakobsen, Tage Christensen, Niels B. Olsen, Thomas B. Schrøder, Daniel Fragiadakis, Riccardo Casalini, C. Michael Roland, Jeppe C. Dyre & Kristine Niss


The Prigogine–Defay ratio quantifies how many parameters are needed to fully characterize the glass-transition behaviour of a viscous liquid. For a single parameter, this ratio is unity, but it has never been clear whether any real liquid has such a value. A discovery of a connection between this ratio and the density scaling behaviour of silicone oil suggests it does.

Subject terms: Condensed-matter physics | Statistical physics, thermodynamics and nonlinear dynamics

See also: News and Views by Angell & Klein

Generalized molecular orbital tomography pp822 - 826

C. Vozzi, M. Negro, F. Calegari, G. Sansone, M. Nisoli, S. De Silvestri & S. Stagira


Atomic and molecular gases generate extreme ultraviolet light when excited by pulses of intense laser light. This emission provides information about the inner workings of the molecules and even enables us to map electron orbitals. However, so far molecular orbital tomography has been restricted to simple molecules. A technique that can be applied to more complicated molecules is now unveiled.

Subject terms: Atomic and molecular physics | Optical physics