Entanglement echoes in quantum computation

A suitable method to characterize the stability of pairwise entanglement in quantum computation was introduced by considering the echo of an initially maximally entangled pair of qubits. A forward-backward evolution of an initial state in which two qubits are in a maximally entangled Bell state was performed. It was shown that noise destroys the entanglement of a pair of qubits and produces entanglement between these two qubits and the other qubits of the quantum computer. The results show that perturbations attenuate the pairwise entanglement echo and generate entanglement between these two qubits and the other qubits of the quantum computer.