(18 February 2026 – United States) A single quantum computing attack on a major US bank could cost the American economy trillions of dollars according to a new Citi GPS report.
The Citi Global Perspectives & Solutions (GPS) report Quantum Threat – The Trillion-Dollar Security Race Is On warns that the window to protect the financial system is closing.
The new report highlights growing concern in the financial services industry pushing the sector to apply new cryptographic standards immediately. Rather than asking when quantum computers might arrive, the report focuses on what would happen if today’s encryption systems were compromised at scale and how costly even a short disruption could be.
If an adversary launched a quantum-enabled cyberattack on any of the top five US financial institutions by targeting its access to the Fedwire Funds Service payment system, it could trigger a cascading failure costing the US economy between US$2 trillion and US$3.3 trillion in indirect impacts. This figure represents a decline in real GDP of ten to 17 percent.
According to Citi, 25 percent of Bitcoin supply is potentially quantum-exposed because the associated public keys have already been revealed on-chain. That translates to roughly 4.5 million to 6.7 million bitcoins, worth an estimated US$500 billion at current prices.
“Q-Day is often treated as a future event. From a risk perspective, it is already here. Data stolen today can be decrypted later. Organisations don’t need quantum systems to respond. PQC is deployable today” stated QuSecure Co-Founder and CEO, Rebecca Krauthamer.
“Quantum computing will trigger the largest upgrade of cryptography in human history, far bigger than the Y2K transition” said HorizonX CEO Steve Suarez.
As AI moves rapidly from hype to reality, it is no longer a question on if bank’s should prepare for quantum computing and adopt AI, but how fast and deeply they must embed upgraded capabilities across operations to meet modern customer expectations.
The Tech Mahindra white paper Building the AI-Driven Bank of Tomorrow highlights quantum technologies representing a radical leap in processing power and cryptographic security. With close links to AI, quantum computing will revolutionise machine learning and pattern recognition across vast datasets but also raises the question – are banks truly prepared for such a seismic change?