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DTSTAMP:20260424T181744Z
UID:1756474200@ist.ac.at
DTSTART:20250829T153000
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DESCRIPTION:Speaker: Andrea Trioni\nhosted by Latha Venkataraman\nAbstract:
  Quantum mechanics reveals a world that defies classical determinism\, whe
 re uncertainty\, superposition\, and fluctuations are fundamental aspects.
  Engineering devices that harness these quantum features requires not only
  precision\, but also a deep understanding of how they interact with their
  surrounding environment. Superconducting circuits\, which exploit macrosc
 opic quantum coherence in low-loss superconducting materials\, provide a s
 calable platform for implementing such systems. Among the critical element
 s in these circuits\, superinductors—high-impedance\, dissipation-free i
 nductive components—play a central role by suppressing charge fluctuatio
 ns. They allow quantum states to be delocalized in phase space\, protect q
 ubits from environmental noise\, and facilitate access to phenomena such a
 s dual Josephson physics and ultra-strong coupling regimes.This thesis exp
 lores two complementary implementations of high-impedance circuits: geomet
 ric superinductors\, demonstrating that high impedance can be achieved bey
 ond kinetic inductance\, and Josephson junction chains\, used to investiga
 te both microwave mode properties and DC transport across the superconduct
 ing-to-insulator transition.Part I addresses geometric superinductors. Con
 trary to the common belief that high-impedance superconducting circuits re
 quire kinetic inductance\, we demonstrate that purely geometric designs ca
 n achieve characteristic impedance exceeding the resistance quantum. By ex
 ploiting mutual coupling between adjacent turns\, coil-based inductors ach
 ieve enhanced self-inductance\, creating a reliable platform for qubits an
 d resonators. Modeling\, simulation\, fabrication\, and characterization c
 onfirm that these elements behave as superinductor. With low loss\, high l
 inearity\, and minimal stray capacitance\, these elements are reproducible
 \, free of uncontrolled tunneling events\, and capable of strong magnetic 
 coupling. This establishes geometric superinductors as robust\, single-wav
 e-function superconducting devices suitable for hardware-protected qubits 
 and hybrid systems.Part II presents classical numerical simulations of a Q
 PS circuit to study dual Shapiro steps.Part III extends the investigation 
 of high characteristic-impedance circuit elements to one-dimensional Josep
 hson junction chains\, which act as a quantum simulator for many-body phys
 ics and the superconductor–insulator transition. Different devices are 
 realized on both sides of the DC phase transition\, showing either a super
 current branch or Coulomb blockade at zero bias. The effect of the crossov
 er on microwave modes\, however\, remains insufficiently investigated. Stu
 dying these modes provides insight into the interplay between disorder and
  phase-slip events. Small differences in circuit component sizes determine
  which side of the transition a device falls on\, make these results relev
 ant not only for fundamental understanding but also for the design of quan
 tum devices\, emphasizing the crucial role of the electromagnetic environm
 ent in stabilizing and controlling fragile quantum states.Together\, these
  results illustrate how carefully engineered high characteristic-impedance
  elements provide a link between macroscopic circuits and the inherently u
 ncertain quantum world\, enabling experiments that probe\, control\, and u
 ltimately exploit quantum fluctuations for applications in quantum informa
 tion\, metrology\, solid state physics and beyond.
LOCATION:Office Bldg West / Ground floor / Heinzel Seminar Room (I21.EG.101
 ) and Zoom\, ISTA
ORGANIZER:
SUMMARY:Andrea Trioni: Thesis Defense: High-Impedance Circuits for Mesoscop
 ic Physics. Geometric Superinductors and Insulating Josephson Chains.
URL:https://talks-calendar.ista.ac.at/events/5962
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