Description
Preserving quantum coherence in the presence of environmental noise is a central challenge for quantum technologies. Noise mitigation using spectator qubits (SQs) has recently emerged as a promising approach, enabling indirect probing of the noise without disturbing the data qubit (DQ). However, existing analyses are largely restricted to two-level fluctuator models, typically described by random telegraph processes, which fail to capture the complexity of realistic noise environments arising from multiple fluctuators. In this work, we study SQ-based noise mitigation for DQs subject to general multi-level Markovian fluctuator noise. The noise is modeled as a finite-state stochastic process with arbitrary transition rates, encompassing ensembles of fluctuators and extending beyond the conventional two-level setting. We first derive the coherence dynamics of the DQ under such noise and characterize the resulting decoherence. Building on this framework, we develop a mitigation scheme in which information about the noise is inferred from sequential SQ measurements and used for phase correction. A heuristic adaptive protocol is proposed to dynamically select the measurement time and angle based on the current noise estimate. Numerical simulations demonstrate that the proposed strategy significantly suppresses decoherence under multi-level noise, achieving performance comparable to that in the two-level case despite the increased complexity of the noise process.
| I am the presenting author | Yes |
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