Noise Simulation of a Tunable Fluxonium : Modeling and Analysis of Markovian and Non-Markovian Effects with Open Quantum Systems

Abstract

This thesis presents an open-system simulator of decoherence in a tunable fluxonium device. The simulator incorporates both standard Markovian noise channels and an additional set of near-resonant two-level-system (TLS) defects as explicit quantum degrees of freedom to capture possible memory effects. The fluxonium is modeled as a qutrit to account for leakage, and its dynamics are simulated both at fixed flux biases and along a time-dependent annealing schedule, with the results compared to the corresponding Markovian dynamics. At fixed bias, the effect of the explicit TLSs depends strongly on the operating point: it is negligible where the relevant charge matrix elements are suppressed, but can reduce T1 by over an order of magnitude and produce non-exponential decay where the qutrit couples strongly to the defects. Along the schedule considered here, a coherent operating window is identified in which the evolution is both adiabatic and coherence-preserving; within it, TLS memory effects do not become significant, and Markovian rate estimates suffice to choose the annealing time.