Johri, U.C.Awasthi, Natasha2019-12-062019-12-062019-01http://krishikosh.egranth.ac.in/handle/1/5810136996We establish uncertainty relations between information loss in general open quantum systems and the amount of nonergodicity of the corresponding dynamics. The relations hold for arbitrary quantum systems interacting with an arbitrary quantum environment. The elements of the uncertainty relations are quantified via distance measures on the space of quantum density matrices. The relations hold for arbitrary distance measures satisfying a set of intuitively satisfactory axioms. The relations show that as the nonergodicity of the dynamics increases, the lower bound on information loss decreases, which validates the belief that nonergodicity plays an important role in preserving information of quantum states undergoing lossy evolution. Considering a model of a central qubit interacting with a fermionic thermal bath its reduced dynamics is investigated for the information loss and nonergodicity. Recently, it was argued that the binegativity might be a good quantifier of entanglement for two-qubit states. Like the concurrence and the negativity, the binegativity is also analytically computable quantifier for all two qubits. Based on numerical evidence, it was conjectured that it is a PPT (positive partial transposition) monotone and thus fulfills the criterion to be a good measure of entanglement. This investigation shows its behaviour under noisy channels which indicate that the binegativity is decreasing monotonically with respect to increasing noise. Binegativity is closely connected to the negativity and has closed analytical form for arbitrary two qubits. Our study supports the conjecture that the binegativity is a monotone. The effect of correlated Markovian noise channels on the quantum speed limit of an open system is examined. This is done for correlated dephasing and amplitude damping channels for a two qubit atomic model. Our model serves as a platform for a detailed study of speed of quantum evolution in correlated open systems.ennullThesis