ABSTRACT The Kitaev's phase estimation algorithm (KPEA) serves as a fundamental quantum subroutine in many quantum algorithms. However, the best existing bound for KPEA's performance remains loose, limiting its broader applicability. In this work, we demonstrate the exact, achievable bound for KPEA's performance, which cannot be further optimized in principle. Our exact bound achieves a 60%–70% reduction over the best existing bound. Both rigorous theoretical proof and numerical simulations confirm the optimality of our proposed bound.
Leng et al. (Sun,) studied this question.