Quantum mechanics is the framework that describes how matter and energy behave at very small scales. It explains effects such as superposition, entanglement, and quantization, which are the basis of quantum computers, quantum sensors, and quantum communication systems. In practice, it tells engineers how qubits behave, how measurements disturb delicate states, and why shielding and low-noise environments matter in experiments.
In cyber security, quantum mechanics matters because it can both create and break protections. Quantum computers built on quantum-mechanical principles could eventually weaken widely used public-key cryptography such as RSA and elliptic-curve systems, motivating post-quantum cryptography and migration planning. The same physics also enables defensive tools such as quantum key distribution and quantum random number generation. Real attacks may involve storing encrypted data now for later decryption, while real defenses focus on quantum-resistant algorithms, careful key management, and trustworthy randomness.