Quantum computing is developing quickly but is confronted nowadays with significant technical, economic, and scientific challenges. This contribution summarizes the essential aspects of modern quantum informatics. It serves as a basis for understanding the developments and challenges in the field of quantum computers (QC), quantum communication, and quantum cryptography (QCCC, or Q3C). This subject area will become more relevant in the coming years. This work is intended to help understand the essential concepts, and challenges as well as the state of the art in this pioneering research field. Further advances in scalability, error correction, and software development are required in the mid-term to spread the technology and present its advantages compared to conventional computing clusters. And, although there are currently no suitable algorithms and working with quantum computers is like “shooting sparrows with the cannons”, sustainable practical applications for quantum computers are also to be established.