Quantum Computing
Quantum computing is a type of computing that uses quantum mechanical phenomena, such as superposition and entanglement, to perform calculations.
The security of the current cryptography techniques used in cryptocurrency and other applications, could be seriously threatened by quantum computing. Quantum computers use quantum bits (qubits), which can simultaneously represent 0 and 1, as opposed to conventional computers, which use bits to represent information as either a 0 or 1. This allows quantum computers to execute some tasks far quicker than classical computers.
The possibility that quantum computers could compromise the cryptographic techniques used to protect private keys and transactions in the blockchain, is a serious source of concern for the crypto community.