Probabilistic quantum cloning（PQC） cannot copy a set of linearly dependent quantum states.In this paper,we show that if incorrect copies are allowed to be produced,linearly dependent quantum states may also be cloned by the PQC.By exploiting this kind of PQC to clone a special set of three linearly dependent quantum states,we derive the upper bound of the maximum confidence measure of a set.An explicit transformation of the maximum confidence measure is presented.
We exploit optimal probabilistic cloning to rederive the JS limit.Dependent on the formulation given by the optimal probabilistic cloning,the explicit transformation of a measure of the JS limit is presented.Based on linear optical devices,we propose an experimentally feasible scheme to implement the JS limit measure of a general pair of two nonorthogonal quantum states.The success probability of the proposed scheme is unity.
In this paper, we derive the explicit transformations of the optimal 1→3, 4, 5 phase-covariant cloning in three dimensions, and then generalize them to the cases of 1 → M = 3n, 3n ＋ 1, 3n ＋ 2 （n ≥ 1 integer） cloning. The clone fidelities are coincident with the theoretical bounds found.
