A QPU, or Quantum Processing Unit, is the quantum hardware component of a computer. Unlike a CPU or GPU, it performs operations on qubits, which can represent multiple states at once and must be controlled with very high precision. In practice, a QPU is not a stand-alone replacement for classical computing; it is usually part of a hybrid system where classical processors handle orchestration, data movement, and error management.
QPU matters in cyber security because mature quantum hardware could eventually weaken widely used public-key cryptography such as RSA and ECC. That creates a long-term risk for encrypted data that attackers may collect now and decrypt later. Defenders use the QPU discussion to plan crypto agility, inventory where vulnerable algorithms exist, and prioritize post-quantum cryptography for systems with long secrecy lifetimes. Today, QPUs are still noisy and limited, so their security impact is mainly strategic: they shape how organizations prepare for future cryptographic change.