The scope of this thesis is to present and discuss some experiments related to the quantum phenomenon of entanglement. We start by introducing the two forms of entanglement that we use: energy-time entanglement and single-photon entanglement. We explain how entanglement can be created through the process of spontaneous parametric down conversion in non-linear waveguides. We explain the importance of Bell inequalities and how we can use them to test the nonlocal nature of quantum correlations. The first experiment is a Bell test with spacelike separation, where we explore the possibility that a change in the gravitational field around one of the detection devices could trigger the collapse of the wavefunction, ending the entangled state. In the second one, we test the hypothesis that a superluminal signal defined in a universal privileged reference frame travelling between the detectors could influence the results. Last, we present the first experimental implementation of an entanglement purification protocol using single-photon entanglement and linear optics elements.