Quantum computers pose an existential threat to modern encryption, with Google and IBM stating they will deploy quantum machines powerful enough to break cryptography protecting banking, government IDs, and classified communications within four years, a scenario experts call Q-Day. The "Q" stands for quantum, marking the theoretical moment when these machines can decrypt currently unhackable data. Quantum computers use qubits with values of both one and zero simultaneously, allowing them to evaluate several computations at once and solve problems quickly, making modern encryption ineffective. Google’s CEO Sundar Pichai compared quantum computing to the state of artificial intelligence five years back, and both Google and IBM have said they will be ready with commercially viable quantum technologies by 2030. Cryptocurrency firms face special risk, as Bitcoin and blockchain rely on encryption techniques potentially exploitable by quantum computers. Companies in telecommunications, financial services, and government have started working on 'quantum-safe cryptography techniques' resistant to quantum attack, marking the biggest cryptographic breakthrough since the internet's creation. Researchers acknowledge it could prove a false alarm, but more companies are preparing as if quantum computing is genuinely coming, signaling institutional confidence that Q-Day isn't if but when.