Experimental investigation of the dynamics of entanglement: Sudden death, complementarity, and continuous monitoring of the environment

Abstract

We report on an experimental investigation of the dynamics of entanglement between a single qubit and its environment, as well as for pairs of qubits interacting independently with individual environments, using photons obtained from parametric down-conversion. The qubits are encoded in the polarizations of single photons, while the interaction with the environment is implemented by coupling the polarization of each photon with its momentum. A convenient Sagnac interferometer allows for the implementation of several decoherence channels and for the continuous monitoring of the environment. For an initially-entangled photon pair, one observes the vanishing of entanglement before coherence disappears. For a single qubit interacting with an environment, the dynamics of complementarity relations connecting single-qubit properties and its entanglement with the environment is experimentally determined. The evolution of a single qubit under continuous monitoring of the environment is investigated, demonstrating that a qubit may decay even when the environment is found in the unexcited state. This implies that entanglement can be increased by local continuous monitoring, which is equivalent to entanglement distillation. We also present a detailed analysis of the transfer of entanglement from the two-qubit system to the two corresponding environments, between which entanglement may suddenly appear, and show instances for which no entanglement is created between dephasing environments, nor between each of them and the corresponding qubit: the initial two-qubit entanglement gets transformed into legitimate multiqubit entanglement of the Greenberger-Horne-Zeilinger (GHZ) type.

15 pages, 14 figures; only .ps was working, now .pdf is also available

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Cited by in corpus (9)

• Robustness of quantum discord to sudden death
• Classical and quantum correlations under decoherence
• Tri-partite Entanglement Witnesses and Sudden Death
• Robustness of Highly Entangled Multi-Qubit States Under Decoherence
• Entanglement evolution of two remote and non-identical Jaynes-Cummings atoms
• Sudden death of distillability in qutrit-qutrit systems
• Scalability of GHZ and random-state entanglement in the presence of decoherence
• Environment-induced entanglement with a single photon
• Sudden death and birth of entanglement beyond the Markovian approximation