Tetrapartite entanglement of fermionic systems in noninertial frames

Under the single-mode approximate, we theoretically investigate the properties of entanglement for four-mode Fermi GHZ state when some observers are in uniform acceleration with respective to others. We use two different definitions for calculating the degree of entanglement. i.e., the arithmetic and geometric average of tangles. It is shown that a maximally entangled state in an inertial frame shall become one with less entanglement in noninertial frame and the partial and the whole entanglements decrease as the number of accelerated observers. In particular, for 1-3 accelerated observers, there is still entanglement in the limit of infinite acceleration for all tangles. However, the sudden death shall be present for both the whole and the part one only when four observers are accelerated. In addition, we make a comparison for these two definitions of entanglement. It is interesting to notice that, for three accelerated observers, the difference first increases and then decreases as the increasing parameter r. (C) 2016 Elsevier GmbH. All rights reserved.