@phdthesis{15101, abstract = {The coupling between presynaptic Ca2+ channels and release sensors is a key factor that determines speed and efficacy of synapse transmission. At some excitatory synapses, channel–sensor coupling becomes tighter during development, and tightening is often associated with a switch in the reliance on different Ca2+ channel subtypes. However, the coupling topography at many synapses remains unknown, and it is unclear how it changes during development. To address this question, we analyzed the coupling configuration at the cerebellar basket cell (BC) to Purkinje cell (PC) synapse at different developmental stages, combining biophysical analysis, structural analysis, and modeling. Quantal analysis of BC–PC indicated that release probability decreased, while the number of functional sites increased during development. Although transmitter release persistently relied on P/Q-type Ca2+ channels in the time period postnatal day 7–23, effects of the Ca2+ chelator EGTA and BAPTA applied by intracellular pipette perfusion decreased during development, indicative of tightening of source-sensor coupling. Furthermore, presynaptic action potentials became shorter during development, suggesting reduced efficacy of Ca2+ channel activation. Structural analysis by freeze-fracture replica labeling (FRL) and transmission electron microscopy (EM) indicated that presynaptic P/Q-type Ca2+ channels formed nanoclusters throughout development, whereas docked vesicles were only clustered at later developmental stages. The number of functional release sites correlated better with the AZ number early in development, but match better with the Ca2+ channel cluster number at later stages. Modeling suggested a developmental transformation from a more random to a more clustered coupling nanotopography. Thus, presynaptic signaling developmentally approaches a point-to-point configuration, optimizing speed, reliability, and energy efficiency of synaptic transmission.}, author = {Chen, JingJing}, issn = {2663-337X}, pages = {84}, publisher = {Institute of Science and Technology Austria}, title = {{Developmental transformation of nanodomain coupling between Ca2+ channels and release sensors at a central GABAergic synapse}}, doi = {10.15479/at:ista:15101}, year = {2024}, } @unpublished{18144, abstract = {High kinetic inductance superconductors are gaining increasing interest for the realisation of qubits, amplifiers and detectors. Moreover, thanks to their high impedance, quantum buses made of such materials enable large zero-point fluctuations of the voltage, boosting the coupling rates to spin and charge qubits. However, fully exploiting the potential of disordered or granular superconductors is challenging, as their inductance and, therefore, impedance at high values are difficult to control. Here we have integrated a granular aluminium resonator, having a characteristic impedance exceeding the resistance quantum, with a germanium double quantum dot and demonstrate strong charge-photon coupling with a rate of $g_\text{c}/2\pi= (566 \pm 2)$ MHz. This was achieved due to the realisation of a wireless ohmmeter, which allows \emph{in situ} measurements during film deposition and, therefore, control of the kinetic inductance of granular aluminium films. Reproducible fabrication of circuits with impedances (inductances) exceeding 13 k$\Omega$ (1 nH per square) is now possible. This broadly applicable method opens the path for novel qubits and high-fidelity, long-distance two-qubit gates.}, author = {Janik, Marian and Roux, Kevin Etienne Robert and Borja Espinosa, Carla N and Sagi, Oliver and Baghdadi, Abdulhamid and Adletzberger, Thomas and Calcaterra, Stefano and Botifoll, Marc and Manjón, Alba Garzón and Arbiol, Jordi and Chrastina, Daniel and Isella, Giovanni and Pop, Ioan M. and Katsaros, Georgios}, booktitle = {arXiv}, title = {{Strong charge-photon coupling in planar germanium enabled by granular aluminium superinductors}}, doi = {10.48550/arXiv.2407.03079}, year = {2024}, } @unpublished{20571, abstract = {We prove the convergence of a modified Jordan--Kinderlehrer--Otto scheme to a solution to the Fokker--Planck equation in $\Omega \Subset \mathbb{R}^d$ with general, positive and temporally constant, Dirichlet boundary conditions. We work under mild assumptions on the domain, the drift, and the initial datum. In the special case where $\Omega$ is an interval in $\mathbb{R}^1$, we prove that such a solution is a gradient flow -- curve of maximal slope -- within a suitable space of measures, endowed with a modified Wasserstein distance. Our discrete scheme and modified distance draw inspiration from contributions by A. Figalli and N. Gigli [J. Math. Pures Appl. 94, (2010), pp. 107--130], and J. Morales [J. Math. Pures Appl. 112, (2018), pp. 41--88] on an optimal-transport approach to evolution equations with Dirichlet boundary conditions. Similarly to these works, we allow the mass to flow from/to the boundary $\partial \Omega$ throughout the evolution. However, our leading idea is to also keep track of the mass at the boundary by working with measures defined on the whole closure $\overline \Omega$. The driving functional is a modification of the classical relative entropy that also makes use of the information at the boundary. As an intermediate result, when $\Omega$ is an interval in $\mathbb{R}^1$, we find a formula for the descending slope of this geodesically nonconvex functional. }, author = {Quattrocchi, Filippo}, booktitle = {arXiv}, keywords = {gradient flows, Jordan–Kinderlehrer–Otto scheme, curves of maximal slope, optimal transport, Dirichlet boundary conditions, Fokker–Planck equation}, title = {{Variational structures for the Fokker-Planck equation with general Dirichlet boundary conditions}}, doi = {10.48550/arXiv.2403.07803}, year = {2024}, } @unpublished{20570, abstract = {We investigate the minimal error in approximating a general probability measure $\mu$ on $\mathbb{R}^d$ by the uniform measure on a finite set with prescribed cardinality $n$. The error is measured in the $p$-Wasserstein distance. In particular, when $1\le p