  When some of the parties of a multipartite entangled pure state are lost, the
question arises whether the residual mixed state is also entangled, in which
case the initial entangled pure state is said to be robust against particle
loss. In this paper, we investigate this entanglement robustness for $N$-qubit
pure states. We identify exhaustively all entangled states that are fragile,
i.e., not robust, with respect to the loss of any single qubit of the system.
We also study the entanglement robustness properties of symmetric states and
put these properties in the perspective of the classification of states with
respect to stochastic local operations assisted with classic communication
(SLOCC classification).

Quantum Physics