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Using the single-mode approximation, we first calculate entanglement measures such as negativity (1 − 3 and 1 − 1 tangles) and von Neumann entropy for a tetrapartite W-Class system in noninertial frame and then analyze the whole entanglement measures, the residual π4 and geometric Π4 average of tangles. Notice that the difference between π4 and Π4 is very small or disappears with the increasing accelerated observers. The entanglement properties are compared among the different cases from one accelerated observer to four accelerated observers. The results show that there still exists entanglement for the complete system even when acceleration r tends to infinity. The degree of entanglement is disappeared for the 1 − 1 tangle case when the acceleration r > 0.472473. We reexamine the Unruh effect in noninertial frames. It is shown that the entanglement system in which only one qubit is accelerated is more robust than those entangled systems in which two or three or four qubits are accelerated. It is also found that the von Neumann entropy S of the total system always increases with the increasing accelerated observers, but the S κξ and S κζδ with two and three involved noninertial qubits first increases and then decreases with the acceleration parameter r, but they are equal to constants 1 and 0.811278 respectively for zero involved noninertial qubit.

We present the entanglement measures of a tetrapartite W-Class entangled system in noninertial frame, where the transformation between Minkowski and Rindler coordinates is applied. Two cases are considered. First, when one qubit has uniform acceleration whilst the other three remain stationary. Second, when two qubits have nonuniform accelerations and the others stay inertial. The 1 − 1 tangle, 1 − 3 tangle and whole entanglement measurements (π4 and Π4), are studied and illustrated with graphics through their dependency on the acceleration parameter r d for the first case and rc and r d for the second case. It is found that the Negativities (1 − 1 tangle and 1 − 3 tangle) and π-tangle decrease when the acceleration parameter r d or in the second case rc and r d increase, remaining a nonzero entanglement in the majority of the results. This means that the system will be always entangled except for special cases. It is shown that only the 1−1 tangle for the first case, vanishes at infinite accelerations, but for the second case the 1 − 1 tangle disappears completely when r > 0.472473. It is found an analytical expression for von Neumann information entropy of the system and we notice that it increases with the acceleration parameter.

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