The quantum computer is ceasing to be a theoretical problem and becoming an issue of technological and financial planning. This was stated by Citigroup in a report published on January 15, 2026, where it warns that the margin of preparation for the so-called Q-day could be reducing.
The report, titled “Quantum threat: The trillion-dollar race for security”, states that preparation no longer revolves solely around when that turning point will arrive, but rather when cost and complexity of migrating current infrastructure to post-quantum cryptography. Citi estimates that this transition could exceed $1 trillion.
Likewise, the financial institution indicates that there is a 19% to 34% chance that Q-day will occur before 2034while by 2044 the estimate increases to a range of 60% to 82%. At the same time, predictive markets like Kalshi assign about 40% probability to the appearance of a useful quantum computer before 2030.
For Citi, the most immediate risk is not a direct future attack, but rather the model known as “harvest now, decrypt later”: malicious actors could store encrypted information today for decipher it when sufficient quantum capacity exists.
It is worth noting that, in the case of cryptocurrencies, the report maintains that the exposure varies depending on the design of each network. In bitcoin (BTC), around 25% of coins would have potential risk because their public keys were already exposed on the chain. For Ethereum, estimate exceeds 65% of current supplywhile in Solana the exhibition would cover practically all assets in circulation.
Finally, Citi also emphasizes that the transition will not be immediate or uniform. The bank points out that regulatory bodies have already begun to define post-quantum cryptography standards and that some governments have set migration goals towards 2030 and 2035 for critical systems. The challenge, he adds, It is not the absence of solutions, but implementing them at scale.
The analysis partially coincides with recent assessments within the Bitcoin ecosystem. As CriptoNoticias reported, a Project Eleven report published in May stated that Q-day could materialize as early as 2030 and compromise up to 6.9 million BTC, equivalent to about 33% of the total supply, especially those associated with old, reused addresses or with visible public keys.
Nevertheless, the scene continues to divide opinions. While reports such as those from Project Eleven and Citi maintain that the adaptation window could shorten during this decade, figures from the bitcoiner ecosystem such as Adam Back, Samson Mow or the developer Murch consider that there would still be many years before there is a quantum computer capable of breaking elliptic curve cryptography in real scenarios.
Until now, much of the discussion has focused on whether Q-day will arrive in 2030, 2033, or later. Citi shifts focus to another problem: how much it will cost to adapt the financial and technological system and decentralized networks before that moment occurs.
If the transition does indeed enter a multi-year, trillion-dollar race, the real risk might not be the arrival of the quantum computer, but running out of time to migrate.