Currently, Ethereum (and most of the internet) relies on cryptographic techniques like ECDSA (Elliptic Curve Digital Signature Algorithm) for security. These are extremely secure— for now. But quantum computers change the game. These machines operate on an entirely different principle than classical computers. Instead of processing one calculation at a time, they use qubits to solve complex problems in parallel. This means they could potentially crack ECDSA encryption in minutes— which would be catastrophic for Ethereum.