Quantum correlations: foundational and practical aspects

Quantum correlations have been an integral if sometimes discomforting aspect of quantum theory for over 85 years. From the early thought-experiments where they were used to argue that quantum mechanics was incomplete, through to their central position as resources in the modern theory of quantum information theory, quantum correlations have proved a hugely rich topic of study. This thesis explores a range of practical and foundational aspects within this ever developing field. Having reviewed fundamental material, we turn to consider the quantum correlations for a task termed anonymous metrology. This is used to demonstrate an operational distinction within the hierarchy of quantum correlations. Building from this we formulate the concept of quantum delocalised interactions, making use of quantum games to study the necessary correlations. With these we establish strong connections to the concurrence monotone and additionally a link with quantum teleportation. We then move to considering entanglement under motion when relativity is accounted for. We demonstrate how the entanglement between internal energy and motional states can be affected by boosts in an analogous way to the known behaviour for spins, and in a more straightforward manner. We then show how this understanding sheds light on the topic of proper time for quantum clocks. Finally we consider a protocol where entanglement can be used to witness non-classicality of gravity. We present improvements which help to bring the scheme closer to experimental feasibility, together with pointing out a potential loophole and how to close it.Open Acces