Quantum Filter: From Dirty Bits to Crystal-Clear Randomness ⚡ экспресс
Cryptography requires truly unpredictable numbers, but physical sources yield biased or correlated bits. Quantum mechanics allows amplifying imperfect randomness to near-perfect, yet previous demonstrations relied on loophole-free Bell tests with spatially co-located devices, limiting remote operation. Certified randomness amplification has been realized in a network on the 98-qubit trapped-ion quantum processor Quantinuum Helios. Quantum gates were applied in real time, state coherence was maintained for about 0.9 s, and measurement bases were communicated to the processor mere milliseconds before measurement, limiting the classical forgery window to 30 ms and the hypothetical adversary’s radius to 4500 km. On random circuits of 64 qubits with 276 two-qubit gates, an accuracy of 0.586 was reached, enabling amplification of a weak random stream with low entropy rate to practically perfect randomness. The protocol remains secure even if the remote device is compromised, provided that sampling occurs faster than classical simulation of quantum circuits is possible.
Modern encryption is unthinkable without truly random numbers. But a standard source can be unreliable or even deliberately corrupted. The solution came from experimenters who built a 98-ion quantum processor—it works like a high-speed filter, turning a 'dirty' signal into one that's crystal-clear and unpredictable. Underpinning this are the discoveries of John Stewart Bell, Alain Aspect, and Anton Zeilinger about quantum entanglement—an instantaneous connection between particles across any distance. Ions inside the processor become entangled and then are measured in a random order, which becomes known only milliseconds before measurement. Due to the speed of light, any interference from more than 4,500 km away couldn't reach the processor within the allotted 30 milliseconds. Even a supercomputer right next to the source would be powerless to slip in a fake. This way, a weak, predictable stream gains high entropy—a measure of unpredictability. The experiment carried out such purification remotely for the first time, confirming that we can only trust randomness when it rests on the foundation of the Standard Model and its quantum laws.
🎯 Previously, amplifying randomness required the source and detector to be in the same lab. This experiment did it remotely for the first time, paving the way for global quantum cryptography.