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Half a century after the inception of the term “successful aging (SA),” a consensus definition has not emerged. The current study aims to provide a comprehensive snapshot of operational definitions of SA. A systematic review across MedLine, PsycInfo, CINAHL, EMBASE, and ISI Web of Knowledge of quantitative operational definitions of SA was conducted. Of the 105 operational definitions, across 84 included studies using unique models, 92.4% (97) included physiological constructs (e.g. physical functioning), 49.5% (52) engagement constructs (e.g. involvement in voluntary work), 48.6% (51) well-being constructs (e.g. life satisfaction), 25.7% (27) personal resources (e.g. resilience), and 5.7% (6) extrinsic factors (e.g. finances). Thirty-four definitions consisted of a single construct, 28 of two constructs, 27 of three constructs, 13 of four constructs, and two of five constructs. The operational definitions utilized in the included studies identify between <1% and >90% of study participants as successfully aging. The heterogeneity of these results strongly suggests the multidimensionality of SA and the difficulty in categorizing usual versus successful aging. Although the majority of operationalizations reveal a biomedical focus, studies increasingly use psychosocial and lay components. Lack of consistency in the definition of SA is a fundamental weakness of SA research.

This study explicates the concept of financial literacy, which has blossomed in use this century. Scholars, policy officials, financial experts and consumer advocates have used the phrase loosely to describe the knowledge, skills, confidence and motivation necessary to effectively manage money. As a result, financial literacy has varying conceptual definitions in existing research, as well as diverse operational definitions and values. This study dissects the differing financial literacy definitions and measures, urging researchers toward common ground. A clearer definition should improve future research, in turn helping consumers better understand and adapt to changing life events and an increasingly complex economy.

Quantum qubits: total recall Two groups this week report a significant step on the long road to quantum computing: the storage and retrieval of single photons onto and from atomic quantum memories. Chanelière et al . produced single photons from an atomic quantum memory in one lab, transported them through a 100-metre-long optical fibre and stored them for a time in a second memory. The atomic excitation was then converted back into a single photon. Previously, weak coherent laser pulses have been stopped and retrieved in atomic media, but single photons are ideal for realizing quantum bits. Eisaman et al . report a similar approach, using the coherent control technique known as electromagnetically induced transparency for the generation, transmission and storage of single photons. A third paper reports progress in another technology critical for quantum communication and computation: the storage and distribution of entangled quantum states. Chou et al . have achieved entanglement between two samples of atoms separated by 2.8 metres that jointly store one quantum bit of information. An elementary quantum network operation involves storing a qubit state in an atomic quantum memory node, and then retrieving and transporting the information through a single photon excitation to a remote quantum memory node for further storage or analysis. Implementations of quantum network operations are thus conditioned on the ability to realize matter-to-light and/or light-to-matter quantum state mappings. Here we report the generation, transmission, storage and retrieval of single quanta using two remote atomic ensembles. A single photon is generated from a cold atomic ensemble at one site 1 , and is directed to another site through 100 metres of optical fibre. The photon is then converted into a single collective atomic excitation using a dark-state polariton approach 2 . After a programmable storage time, the atomic excitation is converted back into a single photon. This is demonstrated experimentally, for a storage time of 0.5 microseconds, by measurement of an anti-correlation parameter. Storage times exceeding ten microseconds are observed by intensity cross-correlation measurements. This storage period is two orders of magnitude longer than the time required to achieve conversion between photonic and atomic quanta. The controlled transfer of single quanta between remote quantum memories constitutes an important step towards distributed quantum networks.

A critical requirement for diverse applications in quantum information science is the capability to disseminate quantum resources over complex quantum networks. For example, the coherent distribution of entangled quantum states together with quantum memory (for storing the states) can enable scalable architectures for quantum computation, communication and metrology. Here we report observations of entanglement between two atomic ensembles located in distinct, spatially separated set-ups. Quantum interference in the detection of a photon emitted by one of the samples projects the otherwise independent ensembles into an entangled state with one joint excitation stored remotely in 10(5) atoms at each site. After a programmable delay, we confirm entanglement by mapping the state of the atoms to optical fields and measuring mutual coherences and photon statistics for these fields. We thereby determine a quantitative lower bound for the entanglement of the joint state of the ensembles. Our observations represent significant progress in the ability to distribute and store entangled quantum states.

Single-photon-added coherent states are the result of the most elementary amplification process of classical light fields by a single quantum of excitation. Being intermediate between a single-photon Fock state (fully quantum-mechanical) and a coherent (classical) one, these states offer the opportunity to closely follow the smooth transition between the particle-like and the wavelike behavior of light. We report the experimental generation of single-photon-added coherent states and their complete characterization by quantum tomography. Besides visualizing the evolution of the quantum-to-classical transition, these states allow one to witness the gradual change from the spontaneous to the stimulated regimes of light emission.

The prospect of realizing entangled quantum states between macroscopic objects and photons 1 has recently stimulated interest in new laser-cooling schemes 2 , 3 . For example, laser-cooling of the vibrational modes of a mirror can be achieved by subjecting it to a radiation 2 or photothermal 4 pressure, actively controlled through a servo loop adjusted to oppose its brownian thermal motion within a preset frequency window. In contrast, atoms can be laser-cooled passively without such active feedback, because their random motion is intrinsically damped through their interaction with radiation 5 , 6 , 7 , 8 . Here we report direct experimental evidence for passive (or intrinsic) optical cooling of a micromechanical resonator. We exploit cavity-induced photothermal pressure to quench the brownian vibrational fluctuations of a gold-coated silicon microlever from room temperature down to an effective temperature of 18 K. Extending this method to optical-cavity-induced radiation pressure might enable the quantum limit to be attained, opening the way for experimental investigations of macroscopic quantum superposition states 1 involving numbers of atoms of the order of 10 14 .

Entangled quantum states are not separable, regardless of the spatial separation of their components. This is a manifestation of an aspect of quantum mechanics known as quantum non-locality 1 , 2 . An important consequence of this is that the measurement of the state of one particle in a two-particle entangled state defines the state of the second particle instantaneously, whereas neither particle possesses its own well-defined state before the measurement. Experimental realizations of entanglement have hitherto been restricted to two-state quantum systems 3 , 4 , 5 , 6 , involving, for example, the two orthogonal polarization states of photons. Here we demonstrate entanglement involving the spatial modes of the electromagnetic field carrying orbital angular momentum. As these modes can be used to define an infinitely dimensional discrete Hilbert space, this approach provides a practical route to entanglement that involves many orthogonal quantum states, rather than just two Multi-dimensional entangled states could be of considerable importance in the field of quantum information 7 , 8 , enabling, for example, more efficient use of communication channels in quantum cryptography 9 , 10 , 11 .

We report on the coherent quantum state transfer from a two-level atomic system to a single photon. Entanglement between a single photon (signal) and a two-component ensemble of cold rubidium atoms is used to project the quantum memory element (the atomic ensemble) onto any desired state by measuring the signal in a suitable basis. The atomic qubit is read out by stimulating directional emission of a single photon (idler) from the (entangled) collective state of the ensemble. Faithful atomic memory preparation and readout are verified by the observed correlations between the signal and the idler photons. These results enable implementation of distributed quantum networking.

Innovation is a key component of most definitions of culture and intelligence. Additionally, innovations may affect a species' ecology and evolution. Nonetheless, conceptual and empirical work on innovation has only recently begun. In particular, largely because the existing operational definition (first occurrence in a population) requires long-term studies of populations, there has been no systematic study of innovation in wild animals. To facilitate such study, we have produced a new definition of innovation: Innovation is the process that generates in an individual a novel learned behavior that is not simply a consequence of social learning or environmental induction. Using this definition, we propose a new operational approach for distinguishing innovations in the field. The operational criteria employ information from the following sources: (1) the behavior's geographic and local prevalence and individual frequency; (2) properties of the behavior, such as the social role of the behavior, the context in which the behavior is exhibited, and its similarity to other behaviors; (3) changes in the occurrence of the behavior over time; and (4) knowledge of spontaneous or experimentally induced behavior in captivity. These criteria do not require long-term studies at a single site, but information from multiple populations of a species will generally be needed. These criteria are systematized into a dichotomous key that can be used to assess whether a behavior observed in the field is likely to be an innovation.

The state of a two-particle system is said to be entangled when its quantum-mechanical wavefunction cannot be factorized into two single-particle wavefunctions. This leads to one of the strongest counter-intuitive features of quantum mechanics, namely non-locality 1 , 2 . Experimental realization of quantum entanglement is relatively easy for photons; a starting photon can spontaneously split into a pair of entangled photons inside a nonlinear crystal. Here we investigate the effects of nanostructured metal optical elements 3 on the properties of entangled photons. To this end, we place optically thick metal films perforated with a periodic array of subwavelength holes in the paths of the two entangled photons. Such arrays convert photons into surface-plasmon waves—optically excited compressive charge density waves—which tunnel through the holes before reradiating as photons at the far side 4 , 5 , 6 , 7 . We address the question of whether the entanglement survives such a conversion process. Our coincidence counting measurements show that it does, so demonstrating that the surface plasmons have a true quantum nature. Focusing one of the photon beams on its array reduces the quality of the entanglement. The propagation of the surface plasmons makes the array effectively act as a ‘which way’ detector.