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arXiv · 2510.05203

Randomness from causally independent processes

Martin Sandfuchs·Carla Ferradini·Renato Renner
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Abstract

We consider a pair of causally independent processes, modelled as the tensor product of two channels, acting on a possibly correlated input to produce random outputs X and Y. We show that, assuming the processes produce a sufficient amount of randomness, one can extract uniform randomness from X and Y. This generalizes prior results, which assumed that X and Y are (conditionally) independent. Note that in contrast to the independence of quantum states, the independence of channels can be enforced through spacelike separation. As a consequence, our results allow for the generation of randomness under more practical and physically justifiable assumptions than previously possible. We illustrate this with the example of device-independent randomness amplification, where we can remove the constraint that the adversary only has access to classical side information about the source.

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Martin Sandfuchs, Carla Ferradini, Renato Renner. 2025-10-06. Randomness from causally independent processes. https://arxiv.org/abs/2510.05203

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