Researchers Explore Quantum Jamming to Test Cryptography Assumptions

Cryptographers are studying the concept of causality to develop communication security methods that remain effective even if quantum mechanics is later replaced by a more complete theory. Quantum key distribution currently relies on the monogamy of entanglement to detect tampering.

If that principle does not hold in a future theory, an external party could change correlations between distant particles without detection.

Physicists describe this undetected change as quantum jamming. The process would allow an outsider to alter entanglement properties while preserving the rule that no information travels faster than light. In a 1990s paper, Jacob Grunhaus, Sandu Popescu, and Daniel Rohrlich outlined how such jamming might work under a no-signaling constraint.

The idea received limited attention until device-independent quantum cryptography protocols became practical in the 2010s.

Ramanathan at the University of Hong Kong and colleagues revisited the 1990s work around 2016. They noted that jamming correlations would break the monogamy assumption used in current device-independent protocols. Michał Eckstein at Jagiellonian University uses a thought experiment with characters Alice, Bob, and a magician to illustrate how jamming could change particle correlations without immediate detection.

Mirjam Weilenmann at Inria and Roger Colbeck at King's College London are using jamming scenarios to refine definitions of cause and effect across different physical theories. "When we work in quantum foundations, what we take very seriously is the no-signaling principle," said Mirjam Weilenmann of the French national research institute Inria.