22,269 research outputs found
Quantum cryptography as a retrodiction problem
We propose a quantum key distribution protocol based on a quantum
retrodiction protocol, known as the Mean King problem. The protocol uses a two
way quantum channel. We show security against coherent attacks in a
transmission error free scenario, even if Eve is allowed to attack both
transmissions. This establishes a connection between retrodiction and key
distribution.Comment: 5 pages, 1 figur
Iterative Optimization of Quantum Error Correcting Codes
We introduce a convergent iterative algorithm for finding the optimal coding
and decoding operations for an arbitrary noisy quantum channel. This algorithm
does not require any error syndrome to be corrected completely, and hence also
finds codes outside the usual Knill-Laflamme definition of error correcting
codes. The iteration is shown to improve the figure of merit "channel fidelity"
in every step.Comment: 5 pages, 2 figures, REVTeX 4; stability of algorithm include
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