According to CoinMeta, research and estimates by quantum computing companies Alice and Bob suggest that a fault-tolerant quantum computer with approximately 29,600 physical qubits could crack the 256-bit elliptic curve cryptography used in Bitcoin within about 1 hour. This study utilized cat and qubits technologies, and the results are theoretical resource estimations; current quantum computers do not yet possess such capabilities. If a sufficiently powerful quantum computer emerges in the future, around 6.9 million Bitcoins could be at risk due to their public keys being known. (Source: bitcoin.com news)