1,721,020 research outputs found
Multimode Quantum Electrodynamics in Structured Photonic Environments
No full textThis thesis explores how engineered bosonic environments in superconducting circuits can be harnessed to control light-matter interaction in regimes that extend beyond conventional cavity quantum electrodynamics (QED).
We develop a scalable platform based on high kinetic inductance superconducting films, enabling the realization of compact, low-disorder coupled cavity arrays (CCAs) with fine spectral control.
This platform is then used to study the dynamics of a giant atom in the superstrong coupling regime, where the coupling of the qubit to mode exceeds the free spectral range of the CCA, .
In the first part of the thesis, we present the design and characterization of high-impedance CCAs using NbN thin films.
This approach allows the implementation of resonators with footprints as small as and impedances of , supporting free spectral ranges from hundreds of MHz down to 5~MHz.
We engineer arrays with up to five resonators per unit cell and realize various band structures, including uniform, dimerized (Su-Schrieffer-Heeger SSH), and multigap configurations.
We quantitatively characterize the CCA disorder using topological edge modes in SSH arrays, developing a likelihood-based method to extract resonator frequency fluctuations.
Measurements on over 25 SSH devices confirm frequency disorder levels of , while maintaining low internal losses () and excellent scalability.
In the second part, we explore multimode QED in the superstrong coupling regime by embedding a transmon qubit into a two-band CCA.
The qubit is non-locally coupled to seven lattice sites, forming a giant atom whose interaction with the bath strongly modifies the spectrum.
Harnessing interference effects between the giant atom and the bath, we reach coupling ratios .
Using a combination of spectroscopy and time-domain measurements, we extract the atomic participation ratio (APR) for all eigenmodes and observe a clear breakdown of the single-mode Jaynes-Cummings model, revealing mode-mode interactions mediated by the qubit.
Furthermore, we investigate directionality in the dressed CCA wavefunction induced by the qubit.
We experimentally demonstrate asymmetric mode localization, leading to directional emission of single-photon states.
By preparing the qubit in a bandgap-localized state and transferring it into the band, we show that emission can be routed predominantly to one side of the array.
This result opens new opportunities for directional quantum optics in engineered superconducting systems.
Together, these results establish high-kinetic inductance CCAs as a powerful platform for analog quantum simulation of impurity models and structured light-matter interactions, offering new pathways to control dissipation, engineer photon-mediated interactions, and probe non-Markovian dynamics in circuit QED.HQ
Fermioni di Majorana in sistemi a due dimensioni?
No full textI fermioni di Majorana sono descritti da soluzioni dell’equazione di Dirac per cui vi è una identificazione tra particella ed antiparticella. A livello fondamentale mancano verifiche sperimentali della loro esistenza in qualità di particelle elementari. Lavori teorici hanno però suggerito la presenza di un loro analogo in sistemi allo stato solido. Recentemente, un primo importante segno della loro esistenza sembra esser stato raggiuntoHQ
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Control and coherence of Loss-DiVincenzo qubits in Si/SiGe quantum dots
No full textElectron spins in Si/SiGe quantum dots are one of the most promising candidates for a quantum bit for their potential to scale up and their long dephasing time. We report for the first time the experimental realization of single electron spin rotations in a single quantum dot (QD) defined in a Si/SiGe 2D electron gas. The electron spin is read out in single-shot mode by a QD charge sensor. Spin rotations are achieved by applying microwave excitation to one of the gates, which oscillates the electron wave function back and forth in the gradient field produced by cobalt micro-magnets fabricated near the dot. By measuring the electron spin resonance frequency as a function of the external magnetic field, the electron g-factor of 1.994 +/- 0.007 is determined. A dephasing time of T2* =850 ns, about 20 times longer than that in GaAs quantum dots, is extracted from the linewidth of the electron spin resonance peak. We observe spin Rabi oscillations with Rabi frequencies up to 5 MHz. Because the coherence time can be longer than the spin manipulation time, we are able to rotate the electron spin even when detuned in frequency, giving the typical chevron pattern when sweeping detuning and microwave burst time. We also realized Ramsey interference experiments, giving a free induction decay T2* = 800 ns. Looking closely, all these data exhibit interference patterns resulting from the contribution of two resonances separated by a frequency difference Δf =2-4 MHz. We tentatively interpret these two resonances as intra-valley spin resonance for two different valley states. Due to the valley-orbit mixing, the orbital wavefunction of each valley state is slightly different, which yields a different Zeeman splitting for each valley state. Finally, we perform Hahn-echo measurement and deduce, for the first time in Si/SiGe, a single spin T2 =37 μs.HQ
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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