If we’re building computers that deal with qubits, superposition and entanglement, wouldn’t these computers also need some way to send qubits to each other? This is the dream of the quantum internet: a network that exchanges quantum-mechanical photons between devices all around the world, parallel to our well-known ‘classical’ internet. 

Anyone who wants to understand the impact of quantum computers, will need to know their basics of cryptography. So let’s start at the beginning.