Impact of decoherence on the metrological advantage of weak-value amplification

We present a theoretical investigation of weak-value amplification (WVA) under decoherence, quantifying its metrological capabilities through the quantum Fisher information (QFI). By modeling decoherence via Kraus operators acting before and after the weak measurement interaction, we derive exact expressions for the QFI governing parameter estimation of a weak coupling strength. These analytical results reveal the fundamental limitation imposed by decoherence on the QFI achievable via WVA. From these results, the optimal post-selection state that maximizes the QFI can be derived for different noise environments. Through paradigmatic examples, including amplitude damping and depolarizing channels, we demonstrate a key distinction: the optimal post-selection evolves with the noise strength in the amplitude damping channel, but is fixed in the depolarizing channel. This work provides both theoretical insights and practical guidance for optimizing metrological schemes based on WVA in realistic decoherent environments.