Qubit interference at avoided crossings: The role of driving shape and bath coupling

We derive the structure of the Landau-Zener-St\"uckelberg-Majorana (LZSM) interference pattern for a qubit that experiences quantum dissipation and is additionally subjected to time-periodic but otherwise general driving. A spin-boson Hamiltonian serves as model which we treat with a Bloch-Redfield master equation in Floquet basis. It predicts a peak structure that depends sensitively on the operator through which the qubit couples to the bath. The Fourier transforms of the LZSM patterns exhibit arc structures which reflect the shape of the driving. These features are captured by an effective time-independent Bloch equation which provides an analytical solution. Moreover, we determine the decay of these arcs as a function of dissipation strength and temperature.Comment: 10 pages, 6 figures, submitted to PR

Entanglement creation in a quantum dot-nanocavity system

We explore the possibility to entangle an excitonic two-level system in a semiconductor quantum dot (QD) with a cavity defined on a photonic crystal by sweeping the cavity frequency across its resonance with the exciton transition. The dynamic cavity detuning is established by a radio frequency surface acoustic wave (SAW). It induces Landau-Zener (LZ) transitions between the excitonic and the photonic degrees of freedom and thereby creates a superposition state. We optimize this scheme by using tailored Fourier-synthesized SAW pulses with up to five harmonics. The theoretical study is performed with a master equation approach for present state-of-the-art setups. Assuming experimentally demonstrated system parameters, we demonstrate that the composed pulses increase both the maximum entanglement and its persistence. The latter is only limited by the dominant dephasing mechanism; i.e., the photon loss from the cavity.Comment: 7 pages, 4 figure

Coherent backscattering of intense light by cold atoms with degenerate energy levels: Diagrammatic treatment

We present a generalization of the diagrammatic pump-probe approach to coherent backscattering (CBS) of intense laser light for atoms with degenerate energy levels. We employ this approach for a characterization of the double scattering signal from optically pumped atoms with the transition $J_g\rightarrow J_e=J_g+1$ in the helicity preserving polarization channel. We show that, in the saturation regime, the internal degeneracy becomes manifest for atoms with $J_g\geq 1$, leading to a faster decrease of the CBS enhancement factor with increasing saturation parameter than in the non-degenerate case.Comment: 18 pages, 16 figure

Employing Circuit QED to Measure Nonequilibrium Work Fluctuations

We study an interferometric method for the measurement of the statistics of work performed on a driven quantum system, which has been put forward recently [Dorner et al., Phys. Rev. Lett. 110 230601 (2013), Mazzola et al., Phys. Rev. Lett. 110 230602 (2013)]. The method allows replacing two projective measurements of the energy of the driven system with qubit tomography of an ancilla that is appropriately coupled to it. We highlight that this method could be employed to obtain the work statistics of closed as well as open driven system, even in the strongly dissipative regime. We then illustrate an implementation of the method in a circuit QED set-up, which allows one to experimentally obtain the work statistics of a parametrically driven harmonic oscillator. Our implementation is an extension of the original method, in which two ancilla-qubits are employed and the work statistics is retrieved through two-qubit state tomography. Our simulations demonstrate the experimental feasibility.Comment: 18 pages, 4 figures. Accepted for publication in New Journal of Physics in the Focus issue on Quantum Microwave Field Effects in Superconducting Circuit

Projections for future radiocarbon content in dissolved inorganic carbon in hardwater lakes: a retrospective approach

Inland water bodies contain significant amounts of carbon in the form of dissolved inorganic carbon (DIC) derived from a mixture of modern atmospheric and pre-aged sources, which needs to be considered in radiocarbon-based dating and natural isotope tracer studies. While reservoir effects in hardwater lakes are generally considered to be constant through time, a comparison of recent and historical DI14C data from 2013 and 1969 for Lake Constance reveals that this is not a valid assumption. We hypothesize that changes in atmospheric carbon contributions to lake water DIC have taken place due to anthropogenically forced eutrophication in the 20th century. A return to more oligotrophic conditions in the lake led to reoxygenation and enhanced terrigenous organic matter remineralization, contributing to lake water DIC. Such comparisons using DI14C measurements from different points in time enable nonlinear changes in lake water DIC source and signature to be disentangled from concurrent anthropogenically induced changes in atmospheric 14C. In the future, coeval changes in lake dynamics due to climate change are expected to further perturb these balances. Depending on the scenario, Lake Constance DI14C is projected to decrease from the 2013 measured value of 0.856 Fm to 0.54–0.62 Fm by the end of the century

Information behavior inside brazilian’s information science dissertations and thesis from 2007-2012: Literature review

Estudos sobre comportamento informacional têm atraído o interesse de diversas áreas do conhecimento, entre elas a Ciência da Informação. Realizou-se uma pesquisa documental exaustiva em âmbito brasileiro, das teses e dissertações apresentadas nos onze Programas de Pós-Graduação de Ciência da Informação, defendidas no período de 2007 a abril de 2012. Foi identificado um total de 465 dissertações e 157 teses publicadas no respectivo período. Ao aplicar a escolha dos seguintes termos no título e palavras-chave: Comportamento Informacional; Comportamento de Busca da Informação; Necessidade de Informação; Estudo de Usuários; Busca da Informação; Acesso à informação; Uso da Informação; Necessidade, Busca, Acesso e Uso da Informação; Sense-Making; Tomada de decisão; e, Recuperação da Informação obteve-se para a análise 88 dissertações e 17 teses. Os termos com maior ocorrência no título foram: Tomada de Decisão (11), Comportamento Informacional (10) e Recuperação da Informação (10). Cabe salientar que, nas palavras-chave a Recuperação da Informação (49) teve a maior ocorrência entre os termos, seguida de Estudo de Usuários (19), Comportamento informacional (15), Necessidade de Informação (12), e Tomada de Decisão (10). A média de 19 documentos publicados por ano entre 2007 e 2010. O estudo identificou os autores, os orientadores e gerou um grafo no qual se percebe o posicionamento central de seis orientadores: Ricardo Barbosa (UFMG), Mônica Erichsen Nassif Borges (UFMG), Murilo Bastos da Cunha (UNB), Emir José Suaiden (UNB), Helen de Castro Silva Casarin (UNESP), Isa Maria Freire (UFF / UFPB). A temática comportamento informacional aparece com maior ocorrência nas instituições: UFMG, UNB, UNESP e UFPB. A pesquisa demonstrou a continuidade de estudos na área e apontaram que aproximadamente 1/5 das dissertações e 1/10 das teses brasileiras abrangem.Studies of information behavior have attracted interest from several areas of knowledge, including information science. We conducted an exhaustive documentary research into dissertations and thesis published in eleven brazilian Post-Graduate Programs in Information Science, from 2007 to april 2012. Were identified a total of 465 thesis and 157 thesis published in the respective period. By applying the choice of the following terms in the title and keywords: Informational Behavior; Information Seeking-Behavior; Information Needs; User Studies; Information Seeking; Information Access; Use of Information; Needs, Seeking, Access and Use of Information; Sense-Making; Decision Making; and Information Retrieval was obtained 88 thesis and 17 dissertations for analysis. The most occurred terms in the title were: Decision Making (11), Information Behavior (10) and Information Retrieval (10). It should be noted that in the keywords Information Retrieval (49) had the highest frequency of occurrence between terms, followed by User Studies (19), Information Behavior (15), Information Needs (12), Decision Making (10). The average between 2007 and 2010 was 19 published papers per year. The study identified the published work advisors and generate a graph which shows the central position of six advisors: Ricardo Barbosa (UFMG), Monica Nassif Erichsen Borges (UFMG), Murilo Bastos da Cunha (UNB), Emir Jose Suaiden ( UNB), Helen de Castro Silva Casarin (UNESP), Isa Maria Freire (UFF / UFPB). The information behavior theme appears with more frequently in the follow institutions: UFMG, UNB, UNESP and UFPB. The survey showed the continuity studies in this area and pointed out that approximately one fifth of thesis and 1/10 of dissertations studies cover this area in Brazil

Gestão de conteúdos em bibliotecas digitais: acesso aberto de periódicos científicos eletrônicos

Argue aspects about contents management in scientific electronic journals at digital libraries, uses the Internet as resource for open access for dissemination, information retrieval and scientific visibility. Digital repositories are essential for scientific documents to dissemination and information retrieval. Focus the publisher of electronic scientific journals, they attributions and trends of the librarian profession. Detail the strategy necessary to management the publishing process

Landau-Zener interference at bichromatic driving

We investigate experimentally and theoretically the interference at avoided crossings which are repeatedly traversed as a consequence of an applied ac field. Our model system is a charge qubit in a serial double quantum dot connected to two leads. Our focus lies on effects caused by simultaneous driving with two different frequencies. We work out how the commensurability of the driving frequencies affects the symmetry of the interference patterns both in real space and in Fourier space. For commensurable frequencies, the symmetry depends sensitively on the relative phase between the two modes, whereas for incommensurable frequencies the symmetry of monochromatic driving is always recovered

Postpartum depressive symptoms in the first 17months after childbirth: the impact of an emotionally supportive partnership

Objectives: This study investigates the impact on different postpartum depressive trajectories (i.e., "non depressive symptoms”, "stable depressive symptoms”, "deterioration” and "improvement”) from 5-17months after childbirth exerted by emotional support that mothers receive from their partners and emotional support they provide to their partners. Methods: Postpartum depressive symptoms were assessed using the Edinburgh Postnatal Depression Scale 5 and 17months after delivery in a sample of 293 mothers. Emotional support received from the partners was assessed among both mothers and partners. Results: The initial level and the change in emotional support that mothers received from their partners were related to different trajectories of postpartum depressive symptoms. Mothers who were living in a partnership with low reciprocal emotional support showed a significantly higher risk of suffering from "stable depressive symptoms” than mothers who were living in a partnership with high reciprocal emotional support. Conclusions: An increased risk of persistent depressive symptoms beyond the early postpartum period was observed in mothers with poor reciprocal emotional support in the partnership. Further research is needed for a better understanding of the mothers persistent depressive symptoms after childbirth associated with reciprocity of emotional support in the partnershi