Quantum computing has long been the boogeyman of Bitcoin security debates. One of ARK Invest’s top crypto researchers now sounds less worried about it.
Lorenzo Valente, ARK’s Director of Research for Digital Assets, says he is more optimistic than he was a year ago that Bitcoin will deploy a quantum fix before “Q Day.” That is the hypothetical moment when a quantum machine becomes strong enough to crack the cryptography protecting Bitcoin addresses.
What Valente is actually saying
Valente’s comments, made in mid-October 2026, mark a change from his view in mid-2025. His outlook tracks a white paper ARK co-authored with Unchained, published on March 12, 2026.
That paper lays out five stages of quantum risk to Bitcoin. The core argument is that the threat builds gradually rather than arriving overnight.
The white paper treats quantum risk as a long-term issue. It does not frame Q Day as a sudden existential event that wipes out Bitcoin in an afternoon.
That gradual timeline is what gives developers room to ship protocol upgrades. Those include post-quantum signature schemes, which are cryptographic methods designed to hold up even against quantum attackers.
The numbers behind the worry
The concern is not purely theoretical. As of October 11, 2026, approximately 7.1 million BTC sits in addresses with exposed public keys.
That is about 35% of the circulating supply. Those coins are considered vulnerable to an attack using Shor’s algorithm, a quantum method that could in theory reverse-engineer private keys from public ones.
Bitcoin relies on elliptic-curve cryptography, or ECC, to prove who owns which coins. Your public key is like a padlock anyone can see, while your private key is the only thing that opens it. Classical computers cannot work backward from the padlock to the key in any useful timeframe. A powerful enough quantum computer running Shor’s algorithm potentially could.
According to the research, a large share of those exposed coins are either regarded as lost or held in addresses that can still migrate to safer setups. Lost coins cannot be moved by their owners anyway. Migratable coins can simply be shifted to quantum-resistant addresses once those exist.
The research also notes that most Bitcoin addresses use hashed versions of public keys. Those are considered resilient to potential quantum attacks, because the actual public key stays hidden until the coins are spent.
Why the hardware is not there yet
Today’s quantum computers operate in what researchers call the Noisy Intermediate-Scale Quantum era, or NISQ. These machines are error-prone and limited in scale.
Current hardware lacks the capability to threaten Bitcoin’s 256-bit ECC. Experts predict it could take years or even decades for quantum technology to cross that threshold.
BIP-360 and the upgrade pipeline
Draft proposals for new output types are under consideration, including BIP-360, aimed at strengthening Bitcoin’s defenses against quantum threats.
According to ARK’s analysis, the Bitcoin ecosystem has shown awareness of the problem and readiness to adopt defensive measures. Ongoing community discussions suggest the solutions are being actively worked on rather than ignored.
What this means for Bitcoin holders
The roughly 35% of supply sitting in exposed addresses is worth tracking. Holders using older address formats or reusing addresses may want to understand their exposure, since those are the coins most likely to need migrating.
Key things to watch include whether BIP-360 advances beyond draft status, how quickly wallets and exchanges support any new output types, and whether quantum hardware makes leaps beyond the NISQ era.
Disclosure: This article was edited by Estefano Gomez. For more information on how we create and review content, see our Editorial Policy.