{"ID":23586793,"CreatedAt":"2026-09-18T05:25:32.833479871Z","UpdatedAt":"2026-09-18T05:25:32.833479871Z","DeletedAt":null,"paper_url":"https://arxiv.org/abs/2609.20133","arxiv_id":"2609.20133","title":"Private communication from Pauli channels with no privacy","abstract":"A channel capacity quantifies the communication capability of a noisy physical process. In contrast to communication channels in the classical world, quantum theory makes this capability contextual. We show that two Pauli two-qubit channels, each with zero private classical capacity, can be used to transmit private information when used together. One is a two-qubit Pauli channel whose environment can reconstruct the receiver output up to matrix transposition; the other is an antidegradable channel. We obtain a similar result when the second channel is the 50% qubit erasure channel. A simple binary code built from rank-three mixtures of Bell states activates private communication. The main ingredient in our construction is a transpose-antidegradable channel that is not antidegradable.","short_abstract":"A channel capacity quantifies the communication capability of a noisy physical process. In contrast to communication channels in the classical world, quantum theory makes this capability contextual. We show that two Pauli two-qubit channels, each with zero private classical capacity, can be used to transmit private inf...","url_abs":"https://arxiv.org/abs/2609.20133","url_pdf":"https://arxiv.org/pdf/2609.20133v1","authors":"[\"Uthirakalyani G\",\"Pritam Halder\",\"David Elkouss\"]","published":"2026-09-17T12:26:28Z","proceeding":"quant-ph","tasks":"[\"quant-ph\"]","methods":"[]","has_code":false}