Enhanced quantum metrology with entangled quantum switch and probe state
Yong-xi Yuan, Cong-Gang Song, Qing-yu Cai · Physica Scripta · 2025
Abstract This study demonstrates that quantum switch can be applied to an entangled system comprising a control qubit and a probe state for parameter estimation, providing additional resources and degrees of freedom to enhance precision. Using a photon probe state as an example, we show that while this approach does not surpass the Heisenberg scaling, it can exceed the Heisenberg bound compared to a definite causal order scheme. For the quantum harmonic oscillator state, when the product of its mass and angular frequency mω is extremely large or extremely small, a suitable encoding method can always be selected to improve the precision. Finally, we demonstrate that if certain operators with specific commutation relations can be realized, the measurement precision has the potential to be further improved.