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A quantum communication experiment represents a significant step towards a global quantum network. These findings have high practical relevance for quantum communications between satellites and ground stations, and may enable large-scale tests of quantum foundations.

WWW.NATURE.COM/NATURE This press release is copyright Nature. VOL.488 NO.7410 DATED 09 AUGUST 2012 This press release contains: · Summaries of newsworthy papers: Fossils: Early hominins weren't picky eaters Comment: Let's talk about sex Earth science: Steps towards understanding water balance Quantum physics: Towards a global quantum network Atmospheric chemistry: Mystery oxidizing agent discovery Physics: Now you see it, now you don’t Marine science: Balancing the ocean nitrogen budget And finally... Squirrels sleep in if it’s too snowy · Mention of papers to be published at the same time with the same embargo · Geographical listing of authors [1] Fossils: Early hominins weren't picky eaters (AOP) DOI: 10.1038/nature11349 An analysis of fossil teeth indicates that Australopithecus, a predecessor of early Homo, had a more varied diet than early Homo and another hominin known as Paranthropus. Signatures of stable isotopes — variants of particular chemical elements — in tooth enamel are used to investigate what South African hominins ate and what their habitat preferences were in a study in Nature this week. These findings add to recent work shedding light on the diet and home ranges of early hominins. It has been suggested that Paranthropus specialized in eating plants; this specialization is thought to have contributed to the demise of Paranthropus by limiting its ability to adapt to changing environmental conditions. Early Homo is thought to have had a more varied diet that included meat. Vincent Balter and colleagues analyse the isotopes in fossil teeth, and their results confirm these proposed diet compositions but show that both of these hominins consumed a less diverse range of foods compared with Australopithecus. They infer that Australopithecus ate both meat and the leaves and fruits of woody plants, and suggest that the composition of this diet may have varied seasonally. Despite the dietary differences, the authors find that the home-range area was of similar size for species of the three hominin genera. CONTACT Vincent Balter (Ecole Normale Supérieure, Lyon, France) Tel: +33 4 72 72 84 88; E-mail: Vincent.Balter@ens-lyon.fr Comment: Let's talk about sex (pp 151-152) The media loves to sensationalize the sexual behaviour of animals — particularly relationships between animals of the same sex — so scientists should describe their research carefully to avoid licentious or inaccurate reporting, warn Andrew Barron and Mark Brown in this week's Nature. To examine how the media portrays relationships between two male rams or two female albatrosses, for instance, Barron and Brown reviewed 48 articles written about the research. They found that most of the articles portrayed the research as documenting gay, lesbian or transgendered behaviour; studies that caused atypical sexual behaviour by genetic or hormonal manipulations were reported as inducing gay or lesbian behaviour or changing the animals' sexual orientation. "To the general public, such inaccurate coverage implies that homosexuality is some sort of illness, which marginalizes a section of human society." They also found, however, that media coverage became less sensational when scientists avoided drawing links between their findings and human behaviour in direct quotes. "The most important advice to scientists working in any area is to maintain a consistent and objective line throughout the paper and in all interactions with the press." CONTACT Andrew Barron (Macquarie University, Sydney, Australia) Tel: +61 2 9850 1310; E-mail: andrew.barron@mq.edu.au Mark Brown (Royal Holloway University of London, UK) Tel: +44 1784 276443; E-mail: Mark.Brown@rhul.ac.uk [2] Earth science: Steps towards understanding water balance (pp 197-200) Humans are overexploiting many large underground water reservoirs, known as aquifers, according to a report in this week’s Nature. The analysis uses a newly developed concept of a ‘groundwater footprint’ to reveal the deficit between aquifer inputs and outputs. This method of calculating the impact of our groundwater consumption on natural stocks and flows could be used to monitor and manage aquifer use. Although unsustainable depletion of groundwater supplies by humans has been documented, it has been difficult to quantify the global scope of the issue. Using the groundwater footprint method to assess water use, Tom Gleeson and colleagues find that globally, humans are currently consuming around 3.5 times the sustainable rate of groundwater renewal. However, they note that the excess withdrawal figure is driven by just a handful of overexploited, agriculturally important aquifers, often situated in arid or semiarid climates. The authors conclude that the groundwater footprint is a powerful tool that could be used to assess the potential of achieving favourable agricultural yields with sustainable groundwater use. CONTACT Tom Gleeson (McGill University, Montreal, Canada) Tel: +1 514 398 6860; E-mail: tom.gleeson@mcgill.ca [3] Quantum physics: Towards a global quantum network (pp 185-188) A quantum communication experiment described in this week’s Nature represents a significant step towards a global quantum network. Optical quantum information is transferred through the atmosphere over greater distances than previously achieved, using advanced acquiring, pointing and tracking techniques. These findings have high practical relevance for quantum communications between satellites and ground stations, and may enable large-scale tests of quantum foundations. The long-distance transfer of quantum information (encoded in unknown states) is essential for the realization of quantum networks. Using the processes of quantum teleportation and entanglement distribution, such transfer has been achieved previously via optical fibre links. However, free-space channels are more promising for long-distance quantum communication, because signal loss and decoherence become fairly negligible in air. Performing experiments across Qinghai Lake in China, Yu-Ao Chen and colleagues report quantum teleportation of independent qubits over 97 km, and demonstrate entanglement distribution over a two-link channel of 101.8 km — potentially enabling a satellite-to-ground scenario. CONTACT Yu-Ao Chen (University of Science and Technology of China, Shanghai, China) Tel: +86 21 6812 0084; E-mail: YuAoChen@ustc.edu.cn [4] Atmospheric chemistry: Mystery oxidizing agent discovery (pp 193-196; N&V) A new oxidizing agent described in Nature this week is shown to have a similar role to oxidants such as ozone in the removal of trace gases, including pollutants, from the atmosphere. The exact identity of this compound remains to be determined, although evidence suggests that forest emissions may be involved in its formation. This compound is capable of oxidizing sulphur dioxide (SO2) and potentially other trace gases, which can drive atmospheric chemistry and influence both air quality and climate. Ozone, the hydroxyl radical and nitrate are considered dominant oxidants involved in the removal of trace gases from the atmosphere; the hydroxyl radical is thought to be the main determinant of SO2 conversion to sulphuric acid. However, measurements of boreal forest sulphuric acid concentrations performed by Roy Mauldin III and colleagues indicate that another oxidant, which they term ‘X’, is involved in the oxidation of SO2. Higher concentrations of X over the hydroxyl radical at night suggest that X may be a stabilized Criegee intermediate, which is formed by a chemical reaction with alkenes emitted from trees, a claim that is substantiated by laboratory experiments. The authors conclude that their data demonstrate a new connection between SO2 emissions, emissions from natural ecosystems, and climate. CONTACT Roy Mauldin III (University of Helsinki, Finland) E-mail: roy.mauldin@helsinki.fi Dwayne Heard (University of Leeds, UK) N&V author E-mail: d.e.heard@leeds.ac.uk [5] Physics: Now you see it, now you don’t (pp 167-171; N&V) A system that can produce unusual optical effects, such as invisibility in one direction, is demonstrated in this week’s Nature. Loss of light is normally seen as a disadvantage in optical metamaterials, standing in the way of useful applications. The new technique, described in this study, shows this disadvantage can be turned around by carefully tuning loss and gain in one system. Ulf Peschel and colleagues borrow a concept from quantum field theory to design new types of artificial optical materials, or metamaterials, with unique properties that do not occur in natural materials. They apply the abstract idea of ‘parity-time symmetry’ to their system, which alters the way light is transported and produces unusual optical behaviour. This idea had previously been discussed, but experimental work in this area had been limited to small-scale systems. The work carried out by Peschel and co-authors, in the temporal domain, is the first experimental observation of light transport in a large-scale synthetic material. CONTACT Ulf Peschel (University of Erlangen-Nürnberg, Germany) Tel: +49 913 1687 7124; E-mail: ulf.peschel@physik.uni-erlangen.de Roberto Morandotti (INRS Center for Energy, Materials and Telecommunications, Varennes, Canada) N&V author Tel: +1 514 228 6924; E-mail: morandot@emt.inrs.ca [6] Marine science: Balancing the ocean nitrogen budget (AOP; N&V) DOI: 10.1038/nature11338 A paper in this week’s Nature reports that during a measurement campaign in the Atlantic Ocean a widely applied method used to measure dinitrogen (N2) fixation rates underestimates these rates relative to measurements made with a recently developed method. An understanding of marine N2-fixation rates is crucial for assessing the future of oceanic primary productivity. Previous attempts to produce a balanced marine nitrogen budget by direct oceanic measurements have proven difficult, with nitrogen loss seemingly exceeding the gain by N2 fixation. Nitrogen is an important nutrient that affects marine productivity; dissolved N2 can only be used by a small number of microorganisms known as diazotrophs, which convert this form into a more biologically active form that other marine life can use. Julie LaRoche and co-workers suggest that the most widely applied method for measuring N2 fixation underestimates N2-fixation rates in the oceanic environment. They compared a traditional method with a recently developed measuring technique in the Atlantic Ocean, and found that N2-fixation rates almost doubled according to the new method. The authors propose that extrapolation of these data to other oceans could nearly double estimates of N2-fixation rates, and could help to close the gap between nitrogen loss and gain. CONTACT Julie LaRoche (Dalhousie University, Halifax, Canada) E-mail: julie.laroche@dal.ca Angelicque White (Oregon State University, Corvallis, OR, USA) N&V author Tel: +1 541 737 6397; E-mail: awhite@coas.oregonstate.edu [7] And finally... Squirrels sleep in if it’s too snowy (AOP) DOI: 10.1038/nature11335 Delays in snow melt in Canada have led to later emergence of Columbian ground squirrels from hibernation, a study in Nature shows this week. This later emergence is implicated in declines in squirrel populations. The most commonly reported ecological effects of climate change are forward shifts in life-cycle events due to warmer spring temperatures. However, Jeffrey Lane and colleagues observe a different response from Columbian ground squirrels to delays in snow melt caused by late-season snowstorms. They find that over the past 20 years, the emergence date of female squirrels has been delayed by nearly half a day each year. This delay is associated with decreased population fitness, which the authors suggest is due to the squirrels having less time to reproduce and accumulate fat before the next hibernation period. The authors conclude that their findings show that responses to climate change are not driven only by warming, and can result in detrimental effects on population viability. CONTACT Jeffrey Lane (University of Edinburgh, UK) Tel: +44 131 650 7287; E-mail: u.columbianus@hotmail.com ADVANCE ONLINE PUBLICATION *** These papers will be published electronically on Nature's website on 08 August at 1800 London time / 1300 US Eastern Time (which is also when the embargo lifts) as part of our AOP (ahead of print) programme. Although we have included them on this release to avoid multiple mailings they will not appear in print on 09 August, but at a later date. *** [8] Division and subtraction by distinct cortical inhibitory networks in vivo DOI: 10.1038/nature11347 [9] Activation of specific interneurons improves V1 feature selectivity and visual perception DOI: 10.1038/nature11312 GEOGRAPHICAL LISTING OF AUTHORS… The following list of places refers to the whereabouts of authors on the papers numbered in this release. For example, London: 4 - this means that on paper number four, there will be at least one author affiliated to an institute or company in London. The listing may be for an author's main affiliation, or for a place where they are working temporarily. Please see the PDF of the paper for full details. CANADA Edmonton: 7 Halifax: 6 Montreal: 2 CHINA Chengdu: 3 Shanghai: 3 FINLAND Helsinki: 4 FRANCE Lyon: 1 Montpellier: 7 Toulouse: 1 GERMANY Bremen: 6 Erlangen: 5 Kiel: 6 Leipzig: 4 NETHERLANDS Utrecht: 2 SOUTH AFRICA Johannesburg: 1 UNITED KINGDOM Edinburgh: 7 UNITED STATES OF AMERICA Alabama Auburn: 7 California Berkeley: 9 Pasadena: 9 Stanford: 9 Colorado Boulder: 4 Florida Orlando: 5 Massachusetts Cambridge: 6, 8, 9 New York Cold Spring Harbor: 9 PRESS CONTACTS… From North America and Canada Neda Afsarmanesh, Nature New York Tel: +1 212 726 9231; E-mail: n.afsarmanesh@us.nature.com From Japan, Korea, China, Singapore and Taiwan Eiji Matsuda, Nature Tokyo Tel: +81 3 3267 8751; E-mail: e.matsuda@natureasia.com From the UK Rebecca Walton, Nature London Tel: +44 20 7843 4502; E-mail: r.walton@nature.com About Nature Publishing Group (NPG): Nature Publishing Group (NPG) is a publisher of high impact scientific and medical information in print and online. NPG publishes journals, online databases and services across the life, physical, chemical and applied sciences and clinical medicine. Focusing on the needs of scientists, Nature (founded in 1869) is the leading weekly, international scientific journal. In addition, for this audience, NPG publishes a range of Nature research journals and Nature Reviews journals, plus a range of prestigious academic journals including society-owned publications. Online, nature.com provides over 5 million visitors per month with access to NPG publications and online databases and services, including Nature News and NatureJobs plus access to Nature Network and Nature Education’s Scitable.com. Scientific American is at the heart of NPG’s newly-formed consumer media division, meeting the needs of the general public. Founded in 1845, Scientific American is the oldest continuously published magazine in the US and the leading authoritative publication for science in the general media. 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