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arXiv · 2603.08204

A Bipartite Quantum Key Distribution Protocol Based on Indefinite Causal Order

Mateusz Leśniak·Ryszard Kukulski·Paulina Lewandowska·Grzegorz Rajchel-Mieldzioć·Michał Wroński
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Abstract

We propose a bipartite quantum key distribution (QKD) protocol based on causal nonseparability: the presence of a resource -- a process matrix -- that does not correspond to any definite causal order between two parties. In our protocol, Alice and Bob perform local operations arranged in a ``causal-order guessing game,'' whereby each round yields an 85.35\% probability of matching bits when the communication is undisturbed. This raw matching probability (or equivalently, a $\sim14.65\%$ error rate) is amenable to standard forward error-correction strategies. We further discuss the practical construction of the QKD protocol using indefinite causal order, where several different scenarios are deeply analyzed.

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Mateusz Leśniak, Ryszard Kukulski, Paulina Lewandowska, Grzegorz Rajchel-Mieldzioć, Michał Wroński. 2026-03-09. A Bipartite Quantum Key Distribution Protocol Based on Indefinite Causal Order. https://arxiv.org/abs/2603.08204

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