Seminar

Quantum entanglement serves as a necessary resource for many quantum information applications. It can be realized between two or more spatially separable parties with the same degree of freedom (interparticle) or within different degrees of freedom of the same particle (intraparticle). However, inevitable interactions with the surroundings result in decoherence, affecting the system in various ways. For an interparticle system, we investigate an interacting two-qubit system coupled with a reservoir under the Markov approximation. Phenomena such as entanglement sudden birth, entanglement sudden death (ESD) and revival of entanglement are observed in evolution of different initial states. It has been shown in the studies that for a vacuum bath, second and third rank mixed states do not exhibit ESD while all fourth rank mixed states exhibit ESD. In applications like quantum teleportation, fourth rank mixed states give high success, it has been shown that among fourth rank states, states with maximum amount of two photon coherence is a better resource for which the time of disentanglement is least. Further, schemes are developed to avoid ESD in some select but important states using local unitary operations. However, under thermal bath conditions, it is observed that ESD is unavoidable in most cases even with the implementation of local unitary operations. Other indicators of nonlocal correlations such as teleportation fidelity exceeding 2/3 and violation of Bell CHSH inequality, also exhibit a sudden loss during evolution, indicating a hierarchy of decay among these nonlocal correlations under decoherence. Furthermore, we investigate an intraparticle pure state with two degrees of freedom, coupled to noise models-amplitude, phase, and depolarizing channels and demonstrated their robustness over interparticle state under decoherence.

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