This thesis presents a set of experiments that explore the possible realisation of a macroscopic quantum network based on solid-state quantum bits. Such a quantum network would allow for studying quantum mechanics on large scales (meters, or even kilometers), and can open new possibilities for applications in quantum information processing. A promising candidate platform for such a network is the nitrogen-vacancy (NV) center in diamond. The NV center is a lattice defect in diamond that has excellent quantum properties and allows optical access to a quantum register of individual electronic and nuclear spins. We use optical spectroscopy and magnetic resonance techniques at liquid helium temperature to manipulate individual spins, and perform projective quantum measurements on them. We first show an experiment in which we create entanglement between two non-interacting nuclear spins by a projective quantum measurement. Second, we demonstrate the creation of an entangled state between two NV electronic spins located in different setups at a distance of three meters. Finally, we demonstrate the deterministic teleportation of the quantum state of a nuclear spin onto an electronic spin over three meters. Our results demonstrate the great potential of the NV center for the realization of a large-scale quantum network.