Which quantum phenomenon limits distance in entanglement-based quantum key distribution (QKD)?

💡 Explanation

When photons travel long distances entanglement-based QKD, decoherence occurs because environmental noise interacts which collapses the entangled state, destroying correlation and preventing secure key exchange. Therefore coherence decay limits distance, rather than depolarization, collapse, or tunneling effects which don't directly break entanglement.

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