92 research outputs found

    Complete eigenstates of identical qubits arranged in regular polygons

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    We calculate the energy eigenvalues and eigenstates corresponding to coherent single and multiple excitations of an array of N identical qubits or two-level atoms (TLA's) arranged on the vertices of a regular polygon. We assume only that the coupling occurs via an exchange interaction which depends on the separation between the qubits. We include the interactions between all pairs of qubits, and our results are valid for arbitrary distances relative to the radiation wavelength. To illustrate the usefulness of these states, we plot the distance dependence of the decay rates of the n=2 (biexciton) eigenstates of an array of 4 qubits, and tabulate the biexciton eigenvalues and eigenstates, and absorption frequencies, line widths, and relative intensities for polygons consisting of N=2,...,9 qubits in the long-wavelength limit.Comment: Added a figure showing how these results can be used to compute deviations from "equal collective decoherence" approximation

    Preparation of decoherence-free, subradiant states in a cavity

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    The cause of decoherence in a quantum system can be traced back to the interaction with the environment. As it has been pointed out first by Dicke, in a system of N two-level atoms where each of the atoms is individually dipole coupled to the environment, there are collective, subradiant states, that have no dipole coupling to photon modes, and therefore they are expected to decay slower. This property also implies that these type of states, which form an N-1 dimensional subspace of the atomic subsytem, also decohere slower. We propose a scheme which will create such states. First the two-level atoms are placed in a strongly detuned cavity and one of the atoms, called the control atom is excited. The time evolution of the coupled atom-cavity system leads to an appropriately entangled state of the atoms. By applying subsequent laser pulses at a well defined time instant, it is possible to drive the atomic state into the subradiant, i. e., decoherence free subspace. Up to a certain average number of the photons, the result is independent of the state of the cavity. The analysis of the conditions shows that this scheme is feasible with present day techniques achieved in atom cavity interaction experiments.Comment: 5 page

    Professions, governance and citizenship through the global looking glass

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    The state-professions relationship and the role of professionalism as facilitator of public sector services are key issues of the professions studies. This makes the study of professions an important source of understanding how to create a “better world,” with more efficient public sectors and accessible services for all citizens. Currently, the relationships between professions and the state face a number of fundamental transformations involving different governance reforms, stakeholders, and professional groups. First, state regulation expands towards “governance” with plural actors and market logics; second, globalization and new economies add new forms of “state” and “citizenship”; and third, austerity politics curb prospering markets and public funding for professional services.info:eu-repo/semantics/publishedVersio

    Collective states in highly symmetric atomic configurations, and single-photon traps

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    Abbreviated Abstract: We study correlated states in a circular and linear-chain configuration of identical two-level atoms containing the energy of a single quasi-resonant photon in the form of a collective excitation, where the collective behaviour is mediated by exchange of transverse photons between the atoms. For a circular configuration of atoms the effective Hamiltonian on the radiationless subspace of the system can be diagonalized analytically. In this case, the radiationless energy eigenstates carry a ZN\mathbb{Z}_N quantum number p=0,1,...,Np=0,1, ..., N which is analogous to the angular momentum quantum number l=0,1,...l= 0, 1, ..., carried by particles propagating in a central potential, such as a hydrogen-like system. Just as the hydrogen s-states are the only electronic wave functions which can occupy the central region of the Coulomb potential, the quasi-particle corresponding to a collective excitation of the circular atomic sample can occupy the central atom only for vanishing ZN\mathbb{Z}_N quantum number pp. For large numbers of atoms in a maximally subradiant state, a critical interatomic distance of λ/2\lambda/2 emerges both in the linear-chain and the circular configuration of atoms. The spontaneous decay rate of the linear configuration exhibits a jump-like "critical" behaviour for next-neighbour distances close to a half-wavelength. Furthermore, both the linear-chain and the circular configuration exhibit exponential photon trapping once the next-neighbour distance becomes less than a half-wavelength, with the suppression of spontaneous decay being particularly pronounced in the circular system. In this way, circular configurations containing sufficiently many atoms may be natural candidates for {\it single-photon traps}.Comment: Invited contribution to "Xth International Conference on Quantum Optics ICQO 2004" in Minsk, Belarus. To be published in Optics and Spectroscop

    The Sub-State Politics of Welfare in Italy: Assessing the Effect of Territorial Mobilization on the Development of Region-Specific Social Governance

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    This article demonstrates that the political mobilization of regional identities through the creation of regionalist parties has positively impacted on the development of region-specific models of welfare governance in Italy. This means that, in a decentralized country, the ‘centre-periphery’ cleavage may significantly influence the sub-state politics of welfare

    Superradiance from an ultrathin film of three-level V-type atoms: Interplay between splitting, quantum coherence and local-field effects

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    We carry out a theoretical study of the collective spontaneous emission (superradiance) from an ultrathin film comprised of three-level atoms with VV-configuration of the operating transitions. As the thickness of the system is small compared to the emission wavelength inside the film, the local-field correction to the averaged Maxwell field is relevant. We show that the interplay between the low-frequency quantum coherence within the subspace of the upper doublet states and the local-field correction may drastically affect the branching ratio of the operating transitions. This effect may be used for controlling the emission process by varying the doublet splitting and the amount of low-frequency coherence.Comment: 15 pages, 5 figure

    El foro romano de <i>Termes (Hispania Citerior)</i>. Síntesis histórica, arqueológica y topográfica. S. I a. C.- s. II d. C.

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    The urban development of the central public area of the Roman city of <i>Termes (Hispania Citerior)</i> between the 1<sup>st</sup> century B.C and the 2<sup>nd</sup> century A.D. is linked to the progressive institutional transformation of the community and to its social and economic development. After the <i>Bellum Sertorianum</i>, the urban space previously occupied by the Celtiberian oppidum was used as a shrine related to one of the founding rites of the city, and which would become the origin of the forum. This area was refurbished during the Augustan era (31 B.C. – 14 A.D.), when a temple was built that overlooked a communal area, although we are not aware of its general layout due to the progressive overlapping of structures in the zone. During the reign of Julius Claudius (14-37 A.D.), a new public area was created, next to the earlier one, which was made up by an arched complex with a temple. This complex was part of a main public area, which was either a Julius Claudius Forum or just an urban sanctuary. Finally, during the Flavian era, from 75 A.D, the site of the Augustan forum would be transformed with the construction of a large scenographic and monumental agora, the Flavian Forum, a complex that would be both a forum and an <i>Augusteum,</i> a place for performances and a shrine for dynastic worship.<br><br>La evolución urbanística del área pública central de la ciudad romana de <i>Termes (Hispania Citerior)</i> entre el s. I a. C. y el s. II d. C. está conectada a la progresiva transformación institucional de la comunidad y a su desarrollo social y económico. Tras el <i>Bellum Sertorianum</i> el espacio urbano ocupado anteriormente por el <i>oppidum</i> celtibérico vio la creación de un santuario relacionado con un rito fundacional de la ciudad, elemento que constituirá el germen del foro. Esta área fue reformada en época augustea (31 a. C.-14 d. C.), con la construcción de un templo que presidía un espacio foral, aunque desconocemos la configuración general de éste último, por la progresiva superposición de estructuras en la zona. Durante la etapa Julio Claudia (14-37 d. C.) se creó una nueva área pública, junto a la anterior, conformada por un recinto porticado con un templo. Este conjunto formaba parte de un espacio público principal, bien un Foro Julio Claudio, bien simplemente un santuario urbano. Finalmente, en época flavia, a partir de 75 d. C., el sitio del foro augusteo será transformado con la construcción de un gran cuadripórtico monumental y escenográfico, el Foro Flavio, complejo que se constituirá, al mismo tiempo, como un foro y un <i>Augusteum</i>, espacio de representación y santuario de culto dinástico

    Disability, support and long-term social care of an elderly Spanish population, 2008-2009: an epidemiologic analysis

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    BACKGROUND: Though poorly known, relationships between disability, need of help (dependency) and use of social services are crucial aspects of public health. The objective of this study was to describe the links between disability, officially assessed dependency, and social service use by an industrial population, and identify areas of inequity. METHODS: We took advantage of a door-to-door survey conducted in the Cinco Villas district, Spain, in 2008–2009, which provided data on disability, morbidity, and service use among 1216 residents aged ≥50 years, and officially assessed dependency under the 2006 Dependency Act (OAD). Using logistic regression, we combined data collected at homes/residences on 625 disability screened-positive participants, and administrative information on degree of OAD and benefits at date of visit. RESULTS: Based on 163 disabled persons, the prevalence of residential/community-care users was 13.4% overall, with 6.0% being market-provided, 2.5% supported by the 2006 Act, and 4.9% supported by other public funds. Of 111 OAD applicants, 30 had been assigned an OAD degree; in 29 cases this was the highest OAD degree, with 12 receiving direct support for residential care and 17 receiving home care. Compared to unassessed dependency, the highest OAD degree was linked to residential care (OR and 95% CI) 12.13 (3.86–38.16), declared non-professional care 10.99 (1.28–94.53), and publicly-funded, non-professional care 26.30 (3.36–205.88). In contrast, 43 persons, 58% of the severely/extremely disabled, community-dwelling sample population, 81% of whom were homebound, including 10 persons with OAD but no implemented service plan, made no use of any service, and of these, 40% lacked a non-professional carer. CONCLUSIONS: Formal service use in the Cinco Villas district attained ratios observed for established welfare systems but the publicly-funded proportion was lower. The 2006 Act had a modest, albeit significant, impact on support for non-professional carers and residential care, coexisting with a high prevalence of non-use of social services by severely disabled persons

    Sulla proposta di istituzione dell’Assegno Unico e Universale per i Figli (AUUF)

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    L'approvazione, imminente, della Legge delega per il varo dell'Assegno unico e universale per i figli (AUUF) rappresenta un importante momento della riforma degli istituti di trasferimento monetario del welfare del nostro paese. Il Gruppo Arel/Feg/Alleanza per l'infanzia intende fornire un proprio contributo nella fase di elaborazione dei Decreti attuativi, proponendosi di ragionare su tale riforma nel presupposto che il testo della Legge delega approvata alla Camera venga approvato in via definitiva al Senato (A.S. n. 1892) senza modificazioni e che i contributi che si vorranno fornire siano rispettosi dei principi contenuti nella Legge delega, pur tenendo conto dei margini di discrezionalità che essa lascia aperti nella produzione dei decreti legislativi
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