2 research outputs found
Correlated Errors in Quantum Error Corrections
We show that errors are not generated correlatedly provided that quantum bits
do not directly interact with (or couple to) each other. Generally, this
no-qubits-interaction condition is assumed except for the case where two-qubit
gate operation is being performed. In particular, the no-qubits-interaction
condition is satisfied in the collective decoherence models. Thus, errors are
not correlated in the collective decoherence. Consequently, we can say that
current quantum error correcting codes which correct single-qubit-errors will
work in most cases including the collective decoherence.Comment: no correction, 3 pages, RevTe
Eavesdropper's Optimal Information in Variations of Bennett-Brassard 1984 Quantum Key Distribution in the Coherent Attacks
We calculate eavesdropper's optimal information on raw bits in
Bennett-Brassard 1984 quantum key distribution (BB84 QKD) and six-state scheme
in coherent attacks, using a formula by Lo and Chau [Science 283 (1999) 2050]
with single photon assumption. We find that eavesdropper's optimal information
in QKD without public announcement of bases [Phys. Lett. A 244 (1998) 489] is
the same as that of a corresponding QKD WITH it in the coherent attack. We
observe a sum-rule concerning each party's information.Comment: no correction, 7 pages, 1 figure, RevTe