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@article{719846, author = {Bouda, Jan and Ziman, Mário}, article_location = {London}, article_number = {20}, keywords = {quantum cryptography; cryptography; encryption; information}, language = {eng}, issn = {0305-4470}, journal = {Journal of Physics A}, title = {Optimality of private quantum channels}, volume = {40}, year = {2007} }
TY - JOUR ID - 719846 AU - Bouda, Jan - Ziman, Mário PY - 2007 TI - Optimality of private quantum channels JF - Journal of Physics A VL - 40 IS - 20 SP - 5415-5426 EP - 5415-5426 PB - IOP Publishing Limited SN - 03054470 KW - quantum cryptography KW - cryptography KW - encryption KW - information N2 - We addressed the question of optimality of private quantum channels. We have shown that the Shannon entropy of the classical key necessary to securely transfer the quantum information is lower bounded by the entropy exchange of the private quantum channel and the von Neumann entropy of the ciphertext state (0). Based on these bounds we have shown that decomposition of private quantum channels into orthogonal unitaries (if they exist) optimizes the entropy. For non-ancillary single-qubit PQC we have derived the optimal entropy for the arbitrary set of plaintexts. In particular, we have shown that except when the (closure of the) set of plaintexts contains all states, one bit key is sufficient. We characterized and analysed all the possible single-qubit private quantum channels for an arbitrary set of plaintexts. For the set of plaintexts consisting of all qubit states we have characterized all possible approximate private quantum channels and we have derived the relation between the security parameter and the corresponding minimal entropy. ER -
BOUDA, Jan and Mário ZIMAN. Optimality of private quantum channels. \textit{Journal of Physics A}. London: IOP Publishing Limited, 2007, vol.~40, No~20, p.~5415-5426, 11 pp. ISSN~0305-4470.
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