Blockstream CEO Adam Back has taken aim at Castle Island Ventures founding partner Nic Carter for drawing attention to what he views as overstated concerns about quantum computing’s impact on Bitcoin.
In a post on X on Friday, Back accused Carter of spreading “uninformed noise” and suggested his comments could be an attempt to influence the market. The remarks came after Carter explained why Castle Island Ventures invested in Project Eleven, a startup focused on safeguarding Bitcoin and other crypto assets against potential quantum computing threats.
Back said the Bitcoin community is not ignoring the issue, emphasizing that research and development around quantum-resistant protections are already underway, albeit “quietly.” Carter pushed back on that characterization, arguing that many Bitcoin developers remain in “total denial” about the risks quantum computing could pose to the network.
Although Castle Island Ventures’ investment only recently regained attention on social media among Bitcoiners, Carter said he first revealed it in an Oct. 20 Substack post. “I disclosed this in the first sentence of my main article on quantum. Can’t get more transparent than that,” he wrote.
Carter explained that his decision to invest was driven by conversations with Project Eleven CEO Alex Pruden, who he said “quantum pilled” him. He added that those discussions made him deeply worried about quantum computing risks to blockchains, prompting him to back the project. “I put capital behind my convictions — always have,” Carter said.
“I knew the bad-faith criticism would come, so I made absolutely sure to be crystal clear about my financial exposure,” Carter added.
Carter outlined several reasons he believes quantum computing represents a real risk to Bitcoin, pointing to governments actively preparing for a post-quantum future, Bitcoin functioning as a kind of “bug bounty” for achieving quantum supremacy, and the growing flow of capital into quantum computing companies.
He is not alone in voicing such concerns. A number of high-profile figures in the Bitcoin space have recently stepped up public warnings about the potential impact of quantum computing on the network.
Some argue the threat could materialize sooner rather than later. Capriole Investments founder Charles Edwards said in an X post on Thursday that quantum computing could pose a serious risk to Bitcoin within the next two to nine years unless the protocol transitions to quantum-resistant cryptography.
Others, however, remain skeptical. Multimillionaire entrepreneur Kevin O’Leary told Cointelegraph Magazine that using quantum computing to crack Bitcoin’s security would be an inefficient application of the technology, suggesting it would be far more valuable for fields such as AI-driven medical research. Back has also struck a more measured tone, saying that while it’s healthy for Bitcoin to become “quantum ready,” quantum computing is unlikely to pose a real threat for decades, given how early and technically limited the technology still is.
