Quantum Filter: From Dirty Bits to Crystal-Clear Randomness express
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.
Original abstract
as written by the authors arXiv:2511.03686
Cryptography depends on truly unpredictable numbers, but physical sources emit biased or correlated bits. Quantum mechanics enables the amplification of imperfect randomness into nearly perfect randomness, but prior demonstrations have required physically co-located, loophole-free Bell tests, constraining the feasibility of remote operation. Here we realize certified randomness amplification across a network by dynamically probing large, entangled quantum states on Quantinuum's 98-qubit Helios trapped-ion quantum processor. Our protocol is secure even if the remote device acts maliciously or is compromised by an intercepting adversary, provided the samples are generated quickly enough to preclude classical simulation of the quantum circuits. We stream quantum gates in real time to the quantum processor, maintain quantum state coherence for $$\approx 0.9$$ seconds, and then reveal the measurement bases to the quantum processor only milliseconds before measurement. This limits the time for classical spoofing to 30 ms and constrains the location of hypothetical adversaries to a $$4{,}500$$ km radius. We achieve a fidelity of 0.586 on random circuits with 64 qubits and 276 two-qubit gates, enabling the amplification of realistic imperfect randomness with a low entropy rate into nearly perfect randomness.
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.