A public dispute has broken out between Blockstream CEO Adam Back and Castle Island Ventures co-founder Nic Carter over whether quantum computing poses a near-term threat to Bitcoin — and how loudly the issue should be discussed.
The exchange played out on X, after Carter explained why Castle Island invested in Project Eleven, a startup working on defenses against potential quantum attacks on Bitcoin and other crypto networks. Carter framed the investment as a response to what he sees as a real and underappreciated risk.
Back wasn’t convinced.
“You make uninformed noise and try to move the market or something. You’re not helping,” Back wrote, pushing back on Carter’s public warnings and suggesting the conversation was being unnecessarily alarmist.
“Quiet work, not public panic”
Back’s core argument is that Bitcoin developers are already thinking about quantum risk — just not in public threads.
He said researchers and engineers are quietly exploring ways to make Bitcoin “quantum ready,” and that turning the issue into a public scare risks distorting the discussion before the technology is even close to being a practical threat.
In Back’s view, quantum computing is still years, if not decades, away from being capable of breaking Bitcoin’s cryptography, and public fear does more harm than good at this stage.
Carter: “Denial is the real risk”
Carter strongly disagreed.
He argued that much of the Bitcoin community is still reluctant to seriously engage with the issue, describing some developers as being in “total denial” about the long-term implications of quantum breakthroughs.
Carter also rejected the idea that he was hiding financial incentives. He said Castle Island’s investment in Project Eleven was disclosed openly weeks earlier, including in the opening lines of 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 said.
Carter described himself as having been “quantum pilled” after discussions with Project Eleven CEO Alex Pruden, saying those conversations convinced him that quantum computing represents a serious — if not immediate — challenge to blockchain security.
“I put capital behind my convictions,” Carter said, adding that he expected criticism and made his exposure clear from the start.
A wider divide in the market
The disagreement highlights a broader split across crypto and investment circles — not over whether quantum computing matters, but when it becomes urgent.
Some investors, like Capriole Investments founder Charles Edwards, have warned that quantum threats could emerge within two to nine years unless Bitcoin adopts quantum-resistant cryptography.
Others are far less concerned. Investor Kevin O’Leary, for example, has argued that using advanced quantum machines to attack Bitcoin would be an inefficient use of the technology, with far greater returns likely in fields like medicine or artificial intelligence.
Back sits firmly in the latter camp. While he agrees Bitcoin should be prepared for a post-quantum future, he continues to describe current fears as premature, calling the technology “ridiculously early” and constrained by major scientific hurdles.
