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Quantum entanglement is a quantum phenomenon that is responsible for novel tasks such as teleportation.  When an initially entangled pair of quantum systems interacts with an environment, there are a number of ways in which the original entanglement can spread throughout the entire multipartite system. IF/UFRJ researchers report theoretical and experimental results regarding the dynamics of the distribution of entanglement in this system. The experiment employs an all optical setup in which the quantum bits are encoded in the polarization degrees of freedom of two photons, and each local interaction is implemented with an interferometer that couples the polarization to the path of each photon, which acts as an environment. They monitor the dynamics and distribution of entanglement and observe the transition from bipartite to multipartite entanglement and back, and show how these transitions are intimately related to the sudden death and sudden birth of entanglement. The multipartite entanglement is further analyzed in terms of three- and four-partite entanglement contributions, and genuine four-qubit entanglement is observed at some points of the evolution.  This work sheds light on the intricate relations between different types of multipartite entanglement, a necessary resource for quantum information networks.

http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.113.240501