Seventeen uses of two broken communication channels can suddenly create a perfect path for information.
Quantum channels with zero capacity are essentially useless for transmitting data. This research describes superactivation, a phenomenon where combining two such channels creates a functional one. The effect occurs much faster than previously theorized, requiring only 17 channel uses to manifest. This is like finding that two empty pipes can suddenly carry water when they are placed next to each other. It opens new doors for building resilient quantum networks using components that were previously considered trash. The impossible becomes possible through simple repetition and combination.
Onset of superactivation of quantum capacity
arXiv · 2604.27042
Superactivation of quantum capacity is the phenomenon whereby two quantum channels, each with zero quantum capacity, can exhibit a strictly positive capacity when used in tandem. In this work, we explore superactivation in the previously unexplored non-asymptotic regime of finitely many channel uses. We give a definition of finite-blocklength superactivation and propose numerical methods that can certify it. Then, focusing on the 50% erasure and positive-partial-transpose channels considered in