Entanglement protection by critical environment

One of the major problems when dealing with quantum systems to be employed in quantum information applications is the loss of coherence due to their interaction with the surrounding environment. When the latter is a many-body system approaching its critical point, though, we can speculate that the associated critical slowing-down could have beneficial effects also on the quantum system of interest, prolonging its quantum coherence. Starting from this idea, we have investigated the dynamics of the entanglement between two qubits, whose environment is modeled as a quantum Ising chain in transverse field, a model that undergoes a quantum phase transition. We found that when a time-dependent applied magnetic field brings the chain into the region around the quantum critical point, and the Kibble-Zurek mechanism arises, the entanglement of the qubit pair is preserved for longer times; the dependence of the dynamics of the concurrence on the relevant model parameters (coupling, chain-length, field quench time) has been investigated