Microsoft quantum leap sharpens Bitcoin risk

Microsoft’s unveiling of its Majorana 2 quantum chip has intensified debate over how quickly Bitcoin and other digital assets must prepare for a post-quantum security era.

The chip, presented at the company’s Build conference in San Francisco, marks the next stage of Microsoft’s long-running push to develop a fault-tolerant quantum computer based on topological qubits. Microsoft says the new processor delivers a sharp improvement over Majorana 1, with qubits that are far more stable and an average lifetime of about 20 seconds, compared with millisecond-scale performance in the earlier generation.

That claim matters beyond the research laboratory because powerful quantum computers could undermine the public-key cryptography used to secure blockchain ownership. Bitcoin’s proof-of-work mining relies on SHA-256 hashing, which is not viewed as the immediate weak point. The greater concern lies with elliptic-curve digital signatures, including ECDSA and Schnorr schemes built around secp256k1, which protect wallet spending authority.

A sufficiently advanced quantum computer running Shor’s algorithm could, in theory, derive a private key from an exposed public key. Once that happens, an attacker could sign a fraudulent transaction and move funds before the legitimate owner can respond. The threat is not practical today, but the timeline has become more contested as major technology groups report progress in hardware stability, error correction and quantum-resource efficiency.

Microsoft has framed Majorana 2 as a step towards commercially useful quantum systems by 2029, putting its roadmap in the same broad window as other industry targets. The company says artificial intelligence tools helped accelerate the chip’s design by improving materials research, parameter setting, testing and diagnostics. A shift in materials, including the use of lead-based superconducting components, is being presented as central to the claimed performance gains.

The announcement has drawn attention across the crypto market because Bitcoin’s security model depends on long-term confidence in cryptographic assumptions. Around 19.7 million bitcoins have already been mined, and a meaningful share sits in addresses where public keys are visible on-chain because coins have been spent from those addresses before. Older pay-to-public-key formats and reused addresses are seen as more exposed than modern address practices that reveal the public key only at the moment of spending.

Quantum-risk specialists have estimated that millions of bitcoins could be at static risk once a cryptographically relevant quantum computer exists. The more difficult scenario involves a live attack during the short window between the broadcast and confirmation of a transaction. Bitcoin’s average block interval of about 10 minutes has therefore become part of the debate, since a quantum attacker would need to derive the private key and submit a competing transaction within that period.

Google-linked research this year added pressure to the discussion by suggesting that fewer quantum resources may be needed to attack 256-bit elliptic-curve systems than older estimates assumed. That has not changed the present-day reality that no publicly known quantum computer can break Bitcoin keys at scale. It has, however, strengthened the case for early migration planning because decentralised networks often take years to agree, test and deploy protocol-level changes.

The scientific response to Microsoft’s topological-qubit programme remains mixed. Supporters view topological qubits as a promising route to lower error rates and more scalable machines. Sceptics argue that claims around Majorana-based devices require more public, reproducible evidence before they can be treated as a confirmed breakthrough. The history of Majorana research includes disputed findings and intense scrutiny over whether observed signals represent true topological states or more ordinary physical effects.

For Bitcoin developers and infrastructure providers, the issue is less whether Majorana 2 alone threatens wallets and more whether it signals faster progress across the quantum industry. Exchanges, custodians and wallet makers face a practical challenge: any transition to post-quantum signatures would have to protect existing holdings, avoid breaking compatibility and maintain confidence during a potentially disruptive migration.