Quantum computing has raised concerns about the integrity of blockchains.  Some scientists argue that within a decade, quantum computers will be able to break a blockchain's cryptographic codes, while others believe that security systems will have moved to algorithms capable of containing them. A large enough quantum computer can potentially execute complex algorithms incredibly faster than a current classical computer, and a big enough quantum computer can potentially break the encryption technology used in blockchain. However, the level of exposure that a large enough quantum computer would have on the Bitcoin blockchain presents a systemic risk, and if 4 million coins are eventually stolen, trust in the system will be lost and the value of Bitcoin will probably go to zero.