Analysis of the entanglement degree between GHZ and W states under continuous measurement

Abstract In most scenarios, particularly when quantum systems are measured to extract information, W states demonstrate greater robustness compared to Greenberger–Horne–Zeilinger (GHZ) states. This study investigates the evolution of entanglement properties in multi-qubit W and GHZ states under continuous measurement. Our findings reveal that, under specific conditions, GHZ states can exhibit superior entanglement properties relative to W states when qubits are measured using a measurement operator. For the three-qubit case, the GHZ state demonstrates stronger entanglement when all three qubits are measured simultaneously. In the four-qubit scenario, the post-measurement entanglement of the GHZ state surpasses that of the W state when the two central qubits are measured simultaneously. Similarly, for the five-qubit system, the GHZ state achieves higher entanglement than the W state when the three central qubits are measured. Furthermore, as the number of qubits increases, the entanglement between qubits in both GHZ and W states diminishes after measurement.