This research field aims to exploit quantum-mechanical phenomena to encode, transmit, manipulate and decode information. Each of these processes takes advantage of underlying quantum principles such as superposition and entanglement and provide a significant advantage over their classical counterpart. Quantum computing promises to solve certain computational problems (for example, integer factorization) substantially faster than by using classical computers. Quantum communication is a field of applied quantum physics closely related to quantum information processing and quantum teleportation: one of the most interesting applications is protecting information channels against eavesdropping by means of quantum cryptography. The most well-known and developed application of quantum cryptography is quantum key distribution, where the presence of an eavesdropper is revealed by the imperfect correlation between the two lists of bits obtained after the transmission of qubits between the emitter and the receiver.