A complex financial contract is like a wager: the payout depends on exchange rates and accrued interest. Physicists would call this uncertainty entropy — a measure of the spread of possible outcomes. To assess the risk, you need to run through all scenarios, like finding every trap-filled dead end in a vast maze. A regular computer methodically checks every twist and turn, wasting hours. A quantum one views the entire maze from above and spots the most dangerous branches.
Researchers split the work: a classical algorithm draws the map, while the quantum one precisely checks the dead ends with rare catastrophic losses. The contract terms were translated into a layout for quantum cells (qubits). In simulations, the error is 1–8%. Surprisingly, noisy, imperfect qubits already outperform classical methods: for risk assessment, it’s more important to cover thousands of scenarios than to calculate each down to the penny. When 300 error-protected qubits become available, the calculation will take a second instead of a week.
A qubit — a quantum cell — combines zero and one, like a coin spinning without falling. This trick allows the computer to process multiple scenarios at once and find an answer in a flash where a regular one would take years.
This resembles psychohistory from Asimov’s 'Foundation' — a mathematics that predicts the fates of civilizations. Only here, instead of galaxies, it’s stock markets.