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news & views coherent transfer determines the amount of no longer suitable for super-activation. states. Engineering different decay channels decoherence; the basis in which the qubit At one further point, they see that the should make it possible to observe a variety is dephased can be controlled using qubit entanglement and distillability with respect of entanglement progressions, which will manipulations performed before and after to all possible 2:2 partitions disappear give us further insights into the of the procedure. This engineered environment but those with respect to any of the 1:3 decoherence and entanglement4. Extending decoheres each qubit independently, but partitions are still present — this is the these techniques could also provide novel with the same strength. signature of bound entanglement. As methods for state and process The team used quantum process more decoherence is introduced, the 1:3 engineering5,6, opening a new playground tomography to reconstruct the full entanglement also disappears, leaving a for quantum science. ❐ of the system for different fully separable state. values of applied decoherence. They Barreiro et al. harness state-of-the-art Jonathan Home is in the Institute for Quantum tested the density matrix for 1:3 and control for generation and manipulation Electronics, ETH Zurich, Hoenggerberg, Zurich 2:2 entanglement, for distillability, for of entangled states, and complement this 8093, Switzerland. violation of a Bell-like inequality and for with a rigorous theoretical analysis. The e-mail: [email protected] its usefulness for ‘entanglement super- controlled progression of multipartite activation’ — a multi-party protocol similar entanglement is made possible by the References 3 to distillation . From this information, admirable precision achieved in the 1. Barreiro, J. T. et al. Nature Phys. 6, 943–946 (2010). they divided up the state evolution during experiments, both in the state initialization 2. Horodecki, M., Horodecki, P. & Horodecki, R. Phys. Rev. Lett. decoherence into regions of different and the engineered decoherence. The study 80, 5239–5242 (1998). properties. The progression is shown not only provides an intriguing view of 3. Shor, P. W., Smolin, J. A. & Thapliyal, A. V. Phys. Rev. Lett. in Fig. 1. As the initial entangled state multipartite entanglement, but also shows 90, 107901 (2003). 4. Aolita, L. et al. Phys. Rev. Lett. 100, 080501 (2008). is decohered, they first observe that the the value of engineered decoherence both 5. Diehl, S. et al. Nature Phys. 4, 878–883 (2008). state stops violating a Bell inequality. for controlling quantum systems and as a 6. Verstraete, F., Wolf, M. M. & Cirac, J. I. Nature Phys. With increasing decoherence the state is tool to understand more about quantum 5, 633–636 (2009).

HISTORY OF The mighty ocean For physics, the first half of the twentieth right). Thomson maintained his centre

century was a time of profound position until the mid-1920s, when enter transformation, bringing about the others, including , c transition from what we now call ‘classical’ , and to ‘modern’ physics. With the new concepts , started to take over. elopment elopment V

and fields of study there emerged a global These changes reflect a shift in e physics community, an ever-growing ‘mainstream’ topics, from and d network of collaboration and scientific , to quantum , exchange. Yves Gingras has analysed to nuclear and solid-state physics. Indeed, hundreds of thousands of scientific papers no single remained in a central esearch and esearch r published between 1900 and 1945, and position in the co-citation network for ge

identified several trends that characterize more than 15 or 20 years. e/ this transformative period (Phys. Perspect. But the first half of the last century was V rchi

12, 248–265; 2010). also a time of radical political upheaval. a In the early years of the twentieth Among the consequences were a decrease century, the sensation of there being what is desired. In fact, this fraction would of German influence in physics and rapid a mountain to climb in exploring and in general be vanishingly small if it weren’t growth in American physics research egrè Visual Visual egrè s understanding the emerging concepts of for the support, through the institution of after the 1920s, as Gingras’s detailed data

and relativity (among our universities, from, on the one hand, the show. On top of these changes, his study aip others) must have been overwhelming. collaboration with colleagues, who advise reveals a steady increase in the number of That such a challenge can be met only where one’s own abilities fail; and, on the and the subdivision of physics through collaborative effort is beautifully other hand, from the education of a young into ever more subfields, together with a captured in the words of , workforce for scientific collaboration.” trend towards publications with several who delivered his inaugural address as Drude was indeed a central figure in the authors, rather than single-author papers. a member of the Prussian Academy of network of physicists of his time. According “Little drops of water, / Little grains Sciences on 28 June 1906 (and committed to the ‘co-citation networks’ constructed by of sand, / Make the mighty ocean / suicide only one week later): “In these Gingras, which capture how often a given And the pleasant land”, says the poem times of rapid progress, when for each author is cited with another, in the periods commonly attributed to the American physicist there are plenty of tasks on 1900–1904 and 1905–1910 Drude was one of Julia Fletcher Carney. It holds some truth for offer, worries also arise that the skill and the most centrally placed physicists, second physics as well. capacity of an individual permits the only to J. J. Thomson (pictured here with achievement of merely a small fraction of , left, and William Coolidge, ANDREAS TRABESINGER

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