Citi Warns of Trillion-Dollar 'Q-Day' Risk as Quantum Computing Threat Looms

NEW YORK – Financial giant Citi has issued a stark warning regarding the approaching "Q-day," the theoretical point at which quantum computers become powerful enough to shatter current public-key encryption standards.

According to a newly released report from the bank, the failure to prepare for this shift could trigger severe economic and geopolitical instability, potentially costing the U.S. economy trillions of dollars. Citi’s analysts estimate a 19% to 34% probability that quantum computers will be capable of widespread encryption breaches by 2034, with that likelihood surging to between 60% and 82% by 2044. The report emphasizes that the fallout would not be contained within a single sector; instead, a successful attack could create a "contagion effect" across the global landscape. Within financial services specifically, quantum attacks threaten to compromise interbank messaging, digital identities, and global payment systems.

The economic projections are particularly grim. Citi suggests that a quantum-led strike on a major American financial institution could result in a $2.0 trillion to $3.3 trillion hit to the U.S. economy in indirect impacts alone. This "GDP-at-risk" scenario represents a potential 10% to 17% decline in annual real GDP, beginning with the initial breach and persisting through a predicted six-month recession. The cryptocurrency market also faces an existential threat, with roughly 25% of all Bitcoin—currently valued at approximately $500 billion to $600 billion—deemed "quantum-exposed."

To mitigate these risks, the bank urges firms to immediately implement structured quantum-readiness programs. Recommended defenses include building "crypto-agile" systems, deploying quantum-safe shields, and transitioning to quantum-ready cloud computing. This transition will require deep collaboration across hardware vendors, software partners, and global supply chains.

Despite the looming deadline, the report offers a note of cautious optimism. Experts point out that the "antidote" to these risks already exists in the form of post-quantum cryptography standards. The primary hurdle facing the global economy is not a lack of technical solutions, but rather the immense logistical difficulty of implementing these protections at scale before quantum capabilities catch up to current defenses.