Animal behaviour Relative size in the mating game

Abstract

As a further test, Chiorescu et al. induced and then analysed coherent Rabi oscillations between the energy levels of the coupled qubit-oscillator system; again, their data are in agreement with expectation. When they prepared the qubit in the ground state, only the Rabi processes associated with this state were visible; similarly, when the qubit was prepared in an excited state, only the Rabi oscillations involving that state were observed (Fig. 1). Although the coherence time was, at most, tens of nanoseconds, the demonstration of time-resolved coherent oscillations in this combined system is a remarkable achievement. The measured frequency of these processes, the Rabi frequency, passed the litmus test-it depended linearly on the amplitude of the microwave that induced the oscillations. Moreover, as the microwave power, and hence the Rabi frequency, was varied, the authors saw a resonance between the Rabi oscillations and the SQUID plasma oscillations,at exactly the position expected. These experiments 2,3 show that a high level of coherence and control is possible in Josephson circuits, such that, on a single chip, qubits could be coupled through the oscillator to create a quantum computer (in the spirit of the coupling in ion-trap quantum registers 8). This is also a step closer to quantum communication-the transfer of quantum information between relatively distant stationary qubits via propagating waves. In both experiments, there is circum-stantial evidence that the qubit and the oscil-lator were entangled; in future work with electronic qubit-oscillator or multi-qubit 7 circuits, it should be possible to observe the degree of entanglement directly. However, this would require the ability to carry out 'single-shot' measurements of both subsystems: although detectors are available that come close to achieving this 5,6,9 , combining all the ingredients into a single circuit and operating it in a coherent regime is a challenge still to be faced. Figure 1 The structure of the energy levels in a coupled qubit-oscillator system, as studied by Wallraff et al. 2 (left) and Chiorescu et al. 3 (right). A common trend in size differences between males and females is a long-standing puzzle. A study of shorebirds shows that the type and strength of competition for mates may explain much of the pattern. F ive decades ago, the German evolutionary biologist Bernhard Rensch 1 presented an intriguing rule for the differing sizes of male and female animals.He found that in several groups (clades) that each contain related species,male size relative to female size increases with the body size of the species. Rensch's rule has since been verified in animals as diverse as arthropods, reptiles, birds and mammals, including primates 2. The causes behind the rule, however, have remained unclear 2-5. Why are males much larger than females in many animals with large body size? And why, in the same clade, are males similar or even smaller than females in species with small body size 1,2 ? As they describe in Proceedings of the National Academy of Sciences, Székely et al. 6 have carried out a comparative analysis of shorebirds that show such trends, and have come up with some thought-provoking conclusions. They show that the trend in sexual 100 YEARS AGO Are they not methodologically equivalent, the three systems of classification-(a) of plants into herbs, shrubs and trees; (b) of animals into birds, beasts and fishes; and (c) of humans into the sanguine, the lymphatic, the bilious and the melancholy? Why, then, is it that science, having long ago given us a Systema Naturae and a nomenclature botanicus and zoologicus, still leaves us almost without the rudiments of a Systema Hominis and a nomenclature sociologicus? It may be asked in reply, What of the anthropologists and their half-century of taxonomic labours in the name of science? But the anthropological classifications belong, in appearance at least, to natural and not human history. They do not rise through psychology into sociology… Of late the anthropologist has shown signs of attaching himself to the psychologist; and this suggests another form of the initial question, Why have anthropologists not endeavoured to formulate even a provisional classification of psychological types? Why have they, with unconscious naïvete, been content to accept implicitly the popular classification that traditionally survives from early Greek thought? To this question the positivist will be ready with his answer, but perhaps it were wiser to leave it as a shameful reminder to the laggard sociologist. From Nature 8 September 1904. 50 YEARS AGO The passing of Prof. T. F. Dreyer has deprived the study of early man in South Africa of one of its acknowledged leaders, and his place will not be easily filled. Outside South Africa, Prof. Dreyer will be most widely remembered as the discoverer of the Florisbad skull, the most remarkable human fossil to be found in Africa since the Broken Hill skull. This discovery was a well-deserved reward for his intuition in selecting for thorough investigation the Florisbad mineral spring deposits with their wealth of archaeological and fossil mammalian remains. But his explorations in the Matjes River Cave and elsewhere also constitute notable contributions to our knowledge of man in South Africa from prehistoric to historic times. With a characteristic scorn for the compartmenting of knowledge, Prof. Dreyer pursued his studies simultaneously in the field of physical anthropology, Quaternary mammalian palaeontology, archaeology and even Quaternary geology and climatology.