Enhancing Non-classical Properties of Entangled Coherent States via Post-Selected von Neumann Measurements

The present study systematically investigates the modulation mechanism of post-selected weak measurement (WM) on the non-classical properties of entangled coherent states (ECSs). The primary goal is achieving controllable enhancement of quantum resources such as entanglement and squeezing, while minimising disturbance to the quantum state. We theoretically analyze the post-selected weak measurement process, and its effectiveness in amplifying the non-classical features of ECSs. The von Neumann measurement model is employed to analytically describe the weak-value amplification of the pointer state. It is demonstrated that a significant enhancement of squeezing can be achieved by tuning the measurement coupling strength. The joint Wigner function analysis in phase space further reveals that, as the coupling strength increases, the coherent structure of the state evolves from symmetric double peaks to multi-branch quantum interference fringes. The entanglement, quantified by the Hillery-Zubairy criterion, exhibits a pronounced increase with stronger coupling, while the quantum Fisher information indicates a systematic improvement in phase estimation precision. The results obtained establish a tunable weak measurement framework for precise manipulation of continuous-variable entangled states. This provides a feasible theoretical pathway for enhancing quantum metrology and measurement-based state engineering.