The Quantum Threat to Ethereum (ETH) Takes Shape: Google Quantum AI Cuts the Risk by 20x

A report published by Google Quantum AI on June 15, 2026 highlights a major advance in quantum computing that could significantly reduce risks for the Ethereum network. According to the researchers, a quantum machine could now break Ethereum's cryptographic signatures with only 205 qubits , compared with 4,096 qubits previously estimated. This algorithmic optimization brings the potential vulnerability window forward from 2035 to 2029 , a critical deadline for the security of the protocol. The facts The Google Quantum AI report reveals that Shor's algorithm, used to break ECDSA -based signatures, could be optimized to require fewer resources than anticipated. Ethereum, which relies on this cryptography to secure its transactions, is therefore more exposed to quantum attacks than expected. The researchers note that this reduction in the number of required qubits makes the threat closer and more tangible for blockchain protocols. For now, Ethereum has not yet deployed a complete post-quantum cryptography solution. The project's GitHub shows 41 commits over the last four weeks, but none specifically concerns a migration to signatures resistant to quantum attacks. Gas fees on the network remain moderate, at 0.0786 gwei on average, but user confidence could be shaken in the long term. Why it matters Ethereum, with a market capitalization of $207.52 billion and a CryptoScore of 76.0/100 , is one of the protocols most vulnerable to quantum risks. A successful attack could allow funds to be stolen or transactions to be forged by deriving private keys from public keys. DeFi protocols such as MakerDAO (DAI) and Compound (COMP) could see their Total Value Locked (TVL) stagnate if confidence in Ethereum's security is called into question. From a regulatory standpoint, authorities could accelerate cybersecurity requirements for blockchains. In Europe, the MiCA standards could incorporate clauses on quantum resistance, requiring protocols to prepare for this threat. Historically, similar vulnerabilities had caused a temporary 5% drop in the price of Bitcoin in 2023, before the market rebounded. Alternatives such as QRL (Quantum Resistant Ledger) , which integrate quantum-resistant signatures by design, could gain appeal compared to Ethereum. However, a complete migration to post-quantum algorithms such as CRYSTALS-Kyber or Dilithium would take several years and would require major updates to nodes and wallets. What to watch The reaction of the Ethereum Foundation is expected by the end of 2026. An official announcement on the next steps for migrating to post-quantum signatures, including a precise timeline, could reassure investors. In addition, hybrid solutions could be developed to allow a gradual transition, thereby limiting risks. Regulators could also play a key role by imposing strict quantum cybersecurity standards. Finally, the price trends of Ethereum and of DeFi protocols on the network will be an indicator of how markets perceive these risks.