Quantum Computing

Quantum computing exploits quantum mechanical phenomena — superposition (a qubit existing as both 0 and 1 simultaneously), entanglement (two qubits instantly correlated regardless of distance), and interference (amplifying correct answers while canceling wrong ones) — to perform certain calculations exponentially faster than classical computers. Theoretical since the 1980s (Richard Feynman, David Deutsch), quantum computers have become practical hardware since 2019 (Google's 'quantum supremacy' demonstration). Current state: IBM has 1,000+ qubit processors; Google achieved quantum supremacy with 53 qubits (2019); China has 66-qubit quantum computers. The key limitation is decoherence — qubits are fragile and lose their quantum state quickly, requiring near-absolute-zero temperatures and extreme isolation. Error correction requires many physical qubits per logical qubit, making truly useful quantum computers requiring millions of physical qubits still years or decades away. Applications: Shor's algorithm would crack RSA encryption (the internet's security backbone) — potentially compromising all encrypted communications. NIST has already started standardizing post-quantum cryptography to prepare.