In this thesis we studied quantum interference and decoherence effects in systems like atoms, ions, quantum dots and photonic waveguides. These systems are presently widely studied in different areas of quantum optics and quantum information sciences. Our investigations showed that trapped ions with j= 1/2 to j=1/2 can be efficient systems where quantum interference effects like the vacuum induced coherences can be studied. We discovered new quantum interference effects induced by spatial variation of laser phase in the Dicke superradiance from atomic or atom like systems. Our investigations also showed the presence of vacuum mediated superexchange and strong quantum correlations in this systems. Further we studied quantum correlations of photons emitted from cascade emission in quantum dots. We showed how the excitonic level splitting and decoherence in the quantum dot can effect such quantum correlations. Moreover we did a detailed analysis of the dynamics of entanglement and environmental decoherence effects for two interacting qubits coupled to several different models of environment. We discovered the phenomenon of bright and dark period in the entanglement dynamics as a result of competing effect of qubit-qubit interactions and environmental decoherence. We also studied entanglement and losses in photonic waveguide for single mode and two mode squeezed states as input. Our investigations showed that waveguides can be potentially useful in generating entanglement and preserving them over time due to their robustness against decoherence. Our investigations hence shows the potential viability's of this novel systems for application in quantum information sciences and opens up important directions in the study of decoherence in such systems.