Degradation of entanglement in moving frames

The distillability of bipartite entangled state as seen by moving observers has been investigated. It is found that the same initial entanglement for a state parameter $\alpha$ and its "normalized partner" $\sqrt{1-\alpha^2}$ will be degraded as seen by moving observer. It is shown that in the ultra relativistic limit, the state does not have distillable entanglement for any $\alpha$.