Due to technical developments in recent years, data security is not sustainable or is only sustainable in combination with new post-quantum approaches. One of these approaches is quantum key exchange (Quantum Key Distribution, QKD). The laws of quantum physics are used to establish a demonstrably physically tap-proof key based on quantum randomness between two parties via a separate quantum channel. An eavesdropping attempt can be detected. Quantum Optics Jena is a German startup that develops and sells complete QKD systems based on polarization-entangled photons for industrial use.