InterJournal Complex Systems, 50
Status: Accepted
Manuscript Number: [50]
Submission Date: 963011
Two-state quantum cryptography with imperfect state preparation
Author(s): Masato Koashi , Nobuyuki Imoto

Subject(s): CX.09

Category: Brief Article


Although it is known that any two nonorthogonal pure states can constitute a secure quantum cryptosystem, the generalization of this scheme to the use of two mixed states is not trivial. It is shown here that even if a condition corresponding to the nonorthogonality in the pure-state case is satisfied, the mixed-state cryptosystem is still vulnerable to attack by an eavesdropper. A necessary and sufficient condition for the secure communication is derived. It states that the two mixed states must be connected by a rotation operator with a nonorthogonal angle.

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