De-excitation dynamics of cold Rydberg atoms

Rydberg atoms (the atoms in excited states with principal quantum number n>20) have very large polarizability (which scales as n^2) and therefore interactions among them (van der Waals) are strong, on the order of about 10MHz for the typical mean interparticle distance of laser-cooled atomic gases (order of micrometer). For this reason, and because of the great control their enhanced properties offer, they have been proposed as simulators of many-body physics. The excitation dynamics through laser light to the Rydberg state in a cold cloud (about 100microkelvin) of Rb atoms has already shown evidences of strong correlations which are a direct consequence of the interactions. Here we present an experimental procedure which yields information on the interactions not through the excitation dynamics, but rather through the dynamics of de-excitation: we add, after the excitation process, a de-excitation phase through a coupling with a rapidly-decaying level and measure the number of remaining excitations as a function of time and of the frequency of the de-excitation laser. A part of the thesis is dedicated to the experimental technique needed for the de-excitation process, which requires a rapid change of the frequency of one of the excitation lasers. We also briefly discuss other techniques involving time-varying frequencies (periodic modulation and sweep) and their application to studies of Rydberg excitation dynamics. The main chapter of this thesis is devoted to the results of the exploration of the de-excitation scheme. We interpret our results in the light of numerical simulations which demonstrate that both the dynamics and the frequency dependence of the de-excitation yield information about the spatial arrangement of the initial Rydberg excitations. We conclude by suggesting possible applications of our procedure, such as the controlled preparation of spatial arrangements of Rydberg excitations by selectively removing a class of atoms at a certain interaction energy

Seeded excitation avalanches in off-resonantly driven Rydberg gases

We report an experimental investigation of the facilitated excitation dynamics in off-resonantly driven Rydberg gases by separating the initial off-resonant excitation phase from the facilitation phase, in which successive facilitation events lead to excitation avalanches. We achieve this by creating a controlled number of initial seed excitations. Greater insight into the avalanche mechanism is obtained from an analysis of the full counting distributions. We also present simple mathematical models and numerical simulations of the excitation avalanches that agree well with our experimental results.Comment: 13 pages, 6 figure

Measuring quantized circular dichroism in ultracold topological matter

The topology of two-dimensional materials traditionally manifests itself through the quantization of the Hall conductance, which is revealed in transport measurements 1–3 .Recently, it was predicted that topology can also give rise to a characteristic spectroscopic response on subjecting a Chern insulator to a circular drive: comparing the frequency-integrated depletion rates associated with drives of opposite orientation leads to a quantized response dictated by the topological Chern number of the populated Bloch band 4,5 .Here we experimentally demonstrate this intriguing topological effect using ultracold fermionic atoms in topological Floquet bands. In addition, our depletion-rate measurements also provide an experimental estimation of the Wannier-spread functional, a fundamental geometric property of Bloch bands related to the quantum metric 6,7 .Our results establish topological spectroscopic responses as a versatile probe, which could be applied to access the geometry and topology of many-body quantum systems, such as fractional Chern insulators 8 .SCOPUS: le.jinfo:eu-repo/semantics/publishe

Measuring quantized circular dichroism in ultracold topological matter

info:eu-repo/semantics/publishe

Resistance to thyrotropin (TSH) in three families is not associated with mutations in the TSH receptor or TSH.

Resistance to TSH (RTSH) is a recently described syndrome of reduced sensitivity to TSH that manifests as euthyroid hyperthyrotropinemia. It is usually identified at birth during routine neonatal screening for congenital hypothyroidism. In less than 2 yr, 13 subjects with RTSH belonging to 8 families have been reported, and all were shown to harbor mutations in the TSH receptor (TSHR) gene. We now report the occurrence of RTSH in 3 unrelated families. Contrary to previous reports, the inheritance of RTSH in 2 of the families was dominant rather than recessive and was not associated with abnormalities in the TSHR gene. Abnormalities in the TSHR gene were excluded by sequencing all coding sequences, exon/intron junctions, and the promoter region of the gene. Furthermore, the involvement of the TSHR in the manifestation of the RTSH phenotype was excluded in 2 families by linkage analysis using intragenic polymorphic markers. We excluded defects in the TSH beta-subunit by sequencing its gene and by showing that the circulating TSH in affected subjects from all families had normal bioactivity. Also, no abnormalities were found in the Gs alpha gene of one family analyzed by GC-clamped denaturing gradient gel electrophoresis. This study shows that RTSH may be a manifestation of several different genetic defects that requires the exploration of other candidate genes involved in the TSH-TSHR-Gs alpha cascade and genes participating in its regulation.Journal ArticleResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, P.H.S.info:eu-repo/semantics/publishe

Emilio FILIERI, Per un nuovo canzoniere. Seicento lirico fra F. Donno, A. Bruni e G. Fontanella, in Convegno Internazionale, Timisoara (Romania), CICCRE-Comunicazione e cultura nella Romània europea-VIa edizione, con il tema 'CANONE CULTURALE. CANONE LETTERARIO. CANONE LINGUISTICO' (organizzato dal Centro di Studi Romanzi di Timisoara-CSRT -Facoltà di Lettere, Storia e Teologia dell'Università di Ovest di Timisoara, in collaborazione con l'Università di Szeged, Ungheria).

Abstract: (Per un nuovo canzoniere. Seicento lirico fra F. Donno, A. Bruni e G. Fontanella) Nel primo Seicento l’approdo alla forma del canzoniere, modulato sul modello tassiano-bembesco, pare profondamente intaccato dall’impatto con le rime mariniane. Interessante così appare lo scorcio sulla lirica meridionale, che non trascura le sedi di Roma e di Venezia, ma che guarda a Napoli come centro di percorsi creativi e di proposte poetiche in versione politematico-emulativa. Autori come A. Bruni, F. Donno e G. Fontanella sembrano risentire inizialmente di una matrice protesa a una tensione sperimentalistica, fra accademie più disponibili alla nuova poetica della varietà-meraviglia e altri sodalizi impregnati del culto riservato al mito tassiano; ma in progresso di tempo alcuni autori non disconobbero le istanze di armonia classicistica acquisite nel contesto napoletano e ripensarono il proprio operare, sino a versi di tenera musicalità. Tra modi mariniani amplificati su una curiosa e libera esplorazione delle potenzialità del codice petrarchistico-bembesco, emergono pure linee interne, che non obliavano la lezione del Tasso per collegarsi alla poetica del Marino in aperture flessibile, illuminate dalle esperienze biografiche individuali, con personali innovazioni distanti dall’epigonismo, nelle rielaborazioni feconde e vivificatrici di un archetipo. Il processo di cambiamento del canone letterario incontrava così la relatività del gusto, in momenti di scarto e di recupero, ma in correlazione con lo spirito mosso e ricco del primo Seicento.'For a new canzoniere. Lyrics of the 17th among F. Donno, A. Bruni and G. Fontanella'-In the first part of the 17th century the portrayal of the canzoniere’s form, modulated on the Tasso-style model, is deeply affected by the impact with the Marino’s rhymes. Interestingly, it looks like the Southern opera, which does not neglect the seats of Rome and Venice, looks at Naples as the center of creative paths and poetic proposals, in a polythematic-emulation fashion. Authors such as A. Bruni, F. Donno, and G. Fontanella appear to be initially affected by a matrix of experimental tension, within the most available academies to the new poetics of wonder/variety or within other impregnated cult cultures to the myth of Tasso; but in the course of time some authors recognized the instances of classicist harmony acquired in the Neapolitan context and rethought their work in tender verses of tender musicality. Among the Marinian ways of amplification, with the effects of skillful virtuosity on a curious and free exploration of the potentials of Petrarca and Bembo code, internal lines also emerge, which did not obey the lesson of the Tasso and were linked to the poetics of Marino in an open and flexible way, also illuminated by individual biographical experiences with personal innovations, which are distant from epigonism, with fruitful re-elaborations of an archetype. The process of changing the literary canon thus met the relativity of taste, in times of waste and recovery, but in correlation with the thrill and rich spirit of the 17th century