Yingzhou Li

The entanglement-assisted Hadamard test (EHT) is a practical method for estimating a quantum phase by amplifying the phase signal. However, the feasible amplification is fundamentally limited by the accuracy of the reference phase, such that the method is inefficient in the high-precision regime.

1 Introduction Knee osteoarthritis (KOA) is a chronic degenerative joint disorder that affects millions of individuals worldwide, particularly older adults. It is characterized by progressive cartilage degradation, subchondral bone changes, and synovial inflammation, leading to pain, stiffness, and functional impairment (Laslett et al., 2024). The condition not only diminishes quality of life but also imposes a significant economic and healthcare burden.