  We study the stability of entanglement in a quantum computer implementing an
efficient quantum algorithm, which simulates a quantum chaotic dynamics. For
this purpose, we perform a forward-backward evolution of an initial state in
which two qubits are in a maximally entangled Bell state. If the dynamics is
reversed after an evolution time $t_r$, there is an echo of the entanglement
between these two qubits at time $t_e=2t_r$. Perturbations attenuate the
pairwise entanglement echo and generate entanglement between these two qubits
and the other qubits of the quantum computer.
