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High accuracy Yb optical lattice clock: frequency comparisons and contributions to International Atomic Time
No full textDuring my PhD at the Politecnico di Torino, I worked at the Italian National Institute of Metrological Research (INRiM) in the field of frequency standards. In particular, in these three years, my research activity has been focused on the improvement and characterization of IT-Yb1, a Ytterbium optical lattice clock developed at INRiM. In the last decades, a great effort has been made to develop optical clocks, which are considered the most promising candidates for the redefinition of the second in the International System of Units (SI). Indeed, optical clocks have the potential to improve by several orders of magnitude the accuracy of the current definition of the second, which is based on the hyperfine transition of the ground state of the Caesium atom.
During these three years, I have succeeded in improving both the accuracy of IT-Yb1 and its robustness. In particular, I have characterized IT-Yb1, achieving a fractional frequency systematic uncertainty of 2×10−17, the smallest uncertainty ever reported for our clock. To reach this goal, I worked on the implementation of an upgraded optical setup for the realization of a vertical optical lattice and on the characterization of several systematic shifts affecting the clock frequency, such as the lattice shift and the DC Stark shift. Moreover, I worked on the robustness and the clock’s reliability, trying to make its operation as continuous as possible. Significantly, in the last two years, IT-Yb1 has proven to be very reliable, operating almost continually for 14 months with an uptime of up to 75% in some weeks.
The highlights of my PhD are summarized in the following. First, an absolute frequency of IT-Yb1 was performed against the primary frequency standard developed at INRiM, the Caesium fountain clock IT-CsF2. In addition, in the last few years, IT-Yb1 has participated in several international comparison campaigns in collaboration with other European and Asian National Metrology Institutes. Furthermore, IT-Yb1 is among the eight optical clocks that have ever submitted data to the Bureau International des Poids et Mesures (BIPM) to contribute to the calibration of the International Atomic Time (TAI). Remarkably, in the last year, IT-Yb1 has regularly contributed to the steering of TAI for 14 consecutive months, showing impressive continuity and robustness. All these results are a clear demonstration of the importance of IT-Yb1 in the international scenario of optical clocks and represent a significant contribution to the future redefinition of the SI second based on an optical standard.
Finally, during the third year of the Ph.D., I spent four months with an Erasmus+Traineeship fellowship at the Laboratoire Charles Fabry in Palaiseau (France), where I worked on the Cyclopix project. In this experiment, the light-scattering of a Rb atomic sample trapped in an optical dipole trap is studied to observe the collective effects in the light emitted by the atoms. This internship was a great opportunity to learn new cooling and trapping techniques, such as optical tweezers, that can be useful for the realization of a new generation of optical clocks
Geometrical errors and their uncertainty in goniophotometers: an application to road surface photometry
Get PDFThe measurement of luminance spatial distribution of road surfaces provides a full description of the light-material interaction.
This quantity is related to road lighting system design and its measurement is performed by goniophotometers. Uncertainty analysis of
goniophotometers is usually performed on laboratory instruments with very low beam divergence. Road surface luminance uncertainty budget needs
a detailed approach because samples are large and due to the size constraints of on-site measurements, portable instruments tend to have larger
beam divergence. In addition, due to the nature of samples, the uncertainty depends on the sample under test. The paper investigates the geometrical
errors implicit in luminance measurements made by goniophotometry in the road surface analysis. It presents a theoretical model of a
goniophotometer for spatial luminance distribution and provides an evaluation of errors dealing with sensors and source optics characteristics
necessary to assess the uncertainty budget of the measurement results
BEST PRACTICE GUIDE: USE OF THERMAL IMAGERS TO PERFORM TRACEABLE NON-CONTACT SCREENING OF HUMAN BODY TEMPERATURE
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Microwave Photon Emission in Superconducting Circuits
No full textQuantum computing requires a novel approach to store data as quantum states, opposite to classical bits. One of the most promising candidates is entangled photons. In this manuscript, we show the photon emission in the range of microwave frequencies of three different types of superconducting circuits, a SQUID, a JPA, and a JTWPA, often used as low-noise parametric amplifiers. These devices can be operated as sources of entangled photons. We report the experimental protocol used to produce and measure microwave radiation from these circuits, as well as data simulations. The collected spectra are obtained by performing single-tone measurements with a direct rf pump on the devices; the output spectra at low powers (below (Formula presented.) dBm) are well interpreted by the dynamical Casimir model, while at high powers (above (Formula presented.) dBm) the system is well described by the Autler–Townes fluorescence of a three-level atom
Scalable and highly selective graphene-based ion-exchange membranes with tunable permselectivity
Get PDFLithobiontic recolonization following cleaning and preservative treatments on the rock engravings of Valle Camonica, Italy: A 54-months monitoring
Get PDF: Both the indirect control of microclimate conditions and the direct application of preservative products to contrast stone bioreceptivity may contribute to limit lithobiontic recolonization of cultural heritage surfaces after cleaning interventions. However, the priority deserved by these different preventive approaches has still been poorly evaluated, particularly in outdoor environments. This work dealt with the engraved sandstone surfaces of the National Park of Rock Engravings of Naquane (Italy, UNESCO WHS), widely colonized by lichens, mosses and a dark cyanobacterial biofilm, and thus requiring frequent cleaning interventions to preserve their legibility for visitors and scholars. In particular, post-cleaning recolonization by the different lithobionts was seasonally monitored along 54 months in different zones of an engraved outcrop, primarily differing in levels of shading, on parcels exposed to nine different conservative treatments. These included (or not) a pre-cleaning devitalization of lithobionts and the post-cleaning application of biocidal (benzalkonium chloride, plant essential oils, usnic acid) and other restoration products (nanocrystalline anatase, polysiloxane-based water repellent, ethyl-silicate-based consolidant). The combination of surface image analyses, fluorimetric and colorimetric measurements showed that mosses and the cyanobacterial biofilm rapidly recolonized all the parcels in the more shaded zone, irrespective of conservative treatments. In the other areas, recolonization significantly differed depending on the treatment. The post-cleaning application of biocides determined the best results through two vegetative seasons, but only nanocrystalline anatase and the polysiloxane-based water repellent maintained the surfaces lighter than uncleaned controls along the whole monitoring period. Recolonization primarily proceeded by the uncleaned surfaces surrounding the parcels and, at least in the examined case of lichens, did not show substantial shifts in community composition, although some nitrophytic species increased their frequency. In conclusion, the effectiveness of preservative treatments to prevent a rapid recolonization of heritage stone surfaces appeared subordinate to the presence of microenvironmental conditions less favourable to lithobionts
Zirconia-Based Ceramics Reinforced by Carbon Nanotubes: A Review with Emphasis on Mechanical Properties
Get PDFThis review outlines the state of the art, processing techniques, and mechanical testing methods of zirconia (ZrO2)-based composites reinforced by carbon nanotubes (CNTs). The use of CNTs as a secondary phase in a zirconia matrix is motivated by their outstanding crack self-healing ability, the possibility to tailor the desired nano-structural properties, and their exceptional wear behavior. Therefore, a detailed investigation into CNT features has been provided. The debate of using the different Vickers indentation fracture toughness equations to estimate the resistance of crack propagation was critically reviewed according to crack characteristics. Finally, this review particularly highlights the exceptional role of ZrO2-based composites as a promising material owing to their outstanding tribo-mechanical properties