Entanglement degradation due to the finite-lifetime of an observer

Entanglement degradation has been previously explored in connection with the Unruh effect, where a bipartite entangled system composed by an inertial observer (Alice), and a uniform acceleration observer (Rob) was studied. The degradation in entanglement between two modes of a non-interacting scalar field is caused by the relative acceleration between the observers. In this work, we show that degradation also occurs when a finite lifetime observer (Dave) is considered instead of the uniformly accelerated observer. The finite lifetime observer is restricted to move in a causal diamond. The system starts in a maximally entangled state, prepared form the perspective of inertial observers, and it becomes less entangled as the lifetime shortens. We argue that this effect is due to the presence of the causal horizons.