PDE and mathematical physics · Oct 6, 2026

Entanglement without distillable secret key

Constructs an entangled state on C10⊗C10\mathbb C^{10}\otimes\mathbb C^{10} with zero distillable secret key for the specified local-instrument protocols that complete almost surely. These allow joint local processing and authenticated two-way public communication, with no other shared private resource and an eavesdropper holding the input purification and public record. A trace-preserving PPT channel on M21(C)M_{21}(\mathbb C) whose square is not entanglement breaking disproves Christandl's PPT-square conjecture.

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