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SEQUENCE:1
UID:UW-Physics-Event-9503
DTSTART:20251201T190000Z
DTEND:20251201T210000Z
DTSTAMP:20260413T083859Z
LAST-MODIFIED:20251121T172111Z
LOCATION:B343 Sterling Hall
SUMMARY:Quantum Electrodynamics of Dual Superconducting Circuits\, Pre
 liminary Exam\, Priya Rajkumar\, Physics PhD Graduate Student
DESCRIPTION:The 2025 Nobel Prize honors the discovery of Macroscopic Q
 uantum Tunneling (MQT). However\, standard superconducting qubits\, su
 ch as the transmon\, are engineered to suppress this phenomenon in a J
 osephson Junction (JJ)\, thereby localizing its phase to create a nonl
 inear inductor. We investigate the opposite regime where MQT prolifera
 tes\, and the junction undergoes a quantum phase transition to an insu
 lating state. Here\, the phase delocalizes while its conjugate variabl
 e—charge—becomes localized\, effectively turning the junction into
  a nonlinear "Bloch" capacitor.
\n
\nWe experimentally realize this un
 derexplored insulating state by galvanically connecting a junction to 
 a high-impedance transmission line composed of thousands of large-area
  JJs. This line achieves characteristic impedances of 5*Resistance qua
 ntum while creating a bath of accessible standing wave modes\, for whi
 ch the junction acts as a nonlinear capacitive termination. Consequent
 ly\, the junction scatters incoming photons\, inducing measurable freq
 uency shifts and spectral broadening. We further combine microwave spe
 ctroscopy with DC excitation to probe charging effects\, such as Coulo
 mb blockade. With our hybrid DC-RF setup\, we elucidate the quantum el
 ectrodynamics of dual superconducting circuits\, which holds promise f
 or advancing quantum circuit theory and metrological techniques.
URL:https://www.physics.wisc.edu/events/?id=9503
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