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.
To suppress decoherence of solid-state qubits which are coupled to the non-Markovian noises, we propose a strategy to couple the qubit with a chaotic device, of which the broad power distribution in the high-frequency domain can be used to freeze the noises just like the dynamical decoupling control (DDC) method. Compared with the DDC, high-frequency components can be generated by the chaotic device even driven by a low-frequency field and we do not need to optimize the control fields to generate complex control pulses. As an application to superconducting circuits, we find that various noises in a wide frequency domain, including low-frequency
1/f, high-frequency Ohmic, sub-Ohmic, and super-Ohmic noises, can be efficiently suppressed by coupling the qubit to a Duffing oscillator, and the decoherence rate of the qubit is efficiently decreased for about 100 times in magnitude.
The research on open quantum systems is important for both quantum computing and quantum sensing. So far, we can only use the main equation to make an approximate description. The dynamics of a single Fluxonium qubit under Markovian environment satisfied Lindblad Master Equation. In experiments, pulse sequence dynamic decoupling (DD) can enhance the coherence of qubits and effectively suppress noise. Two Fluxonium qubits sensitive to two-level systems (TLS) noise. TLS formed by material defects results in noise with significant non-Markovian characteristics. The dynamics of non-Markovian noise satisfied the post Markov Master Equation (PMME). The TLS noise spectrum is mainly concentrated in low frequencies, so traditional DD cannot effectively suppress TLS noise. The relaxation and dephasing behavior with a complex dynamic characteristics. Based on Ornstein-Uhlenbeck process, we put forward a novel DD sequence and design a TLS-tailored dynamical decoupling protocol by optimizing pulse locations to minimize noise power spectral overlap with the Lorentzian shape. Using PMME-consistent framework, we can obtain a stronger low frequency suppression and significantly prolong both Bell-based fidelity and entanglement. We explore specific DD design and precise modeling of entanglement dynamics under non-Markovian TLS noise. Our dynamical decoupling protocol can effectively improve entanglement gates fidelity in NISQ quantum devices.