The trend towards digitalization and the advance of the Internet is changing the world around us. Information has become the crucial resource of modern society and its security essential. Online payment systems, elections and critical infrastructure such as power grids, the health care system and telecommunication networks are vital parts of our lives and must be protected. Cryptography is the means to enable these applications and guarantee the information security needed. However, the rise of quantum computers threatens many of the currently used cryptographic schemes. Yet, the same quantum laws also enable a variety of cryptographic solutions to this issue. They remain secure in the presence of Quantum Computers and can therefore help to protect critical IT systems. Recent years have seen a spike in interest in this technology. Quantum Cryptography is an active field of research and there exist companies producing quantum-cryptographic devices. Nonetheless, there are still several open questions between theory and practice which hinder the more widespread adoption of this technology.