Entanglement dynamics of multi-fluxonium-qubits under non-Markovian TLS noise

Abstract

We examine the entanglement dynamics of two capacitively connected fluxonium qubits influenced by correlated non-Markovian two-level-system (TLS) noise. The environment is represented by an Ornstein–Uhlenbeck process with a Lorentzian spectrum, and the filter-function formalism is utilized as the main framework to assess finite-memory effects and analyze dynamical-decoupling (DD) performance. We design a TLS-oriented DD sequence by optimizing pulse placements within experimentally motivated control limitations for the low-frequency-dominated TLS spectrum pertinent to fluxonium devices. Numerical results indicate that the optimized protocol more efficiently mitigates spectral overlap with TLS noise and enhances the preservation of two-qubit entanglement throughout empirically pertinent timeframes, in comparison to traditional sequences. A succinct post-Markovian master-equation analysis is incorporated solely as a phenomenological consistency verification for the finite-memory crossover. The results establish a quantifiable standard for entanglement preservation in linked fluxonium qubits subjected to colored non-Markovian noise and underscore the need for spectrum-aware DD design for superconducting qubit systems.