Experimental multiparticle entanglement dynamics induced by decoherence

Multiparticle entanglement leads to richer correlations than two-particle entanglement and gives rise to striking contradictions with local realism(1), inequivalent classes of entanglement(2) and applications such as one-way or topological quantum computing(3,4). When exposed to decohering or dissipative environments, multiparticle entanglement yields subtle dynamical features and access to new classes of states and applications. Here, using a string of trapped ions, we experimentally characterize the dynamics of entanglement of a multiparticle state under the influence of decoherence. By embedding an entangled state of four qubits in a decohering environment (through spontaneous decay), we observe a rich dynamics crossing distinctive domains: Bell-inequality violation, entanglement superactivation, bound entanglement and full separability. We also develop new theoretical tools for characterizing entanglement in quantum states. Recent quantum-computing, state-engineering and simulation paradigms driven by dissipative or decohering environments(5-7) can benefit from the environment engineering techniques demonstrated here.