  The classical signal splitting and copying are not possible in quantum
mechanics. Specifically, one cannot copy the basis up and down states of the
input (I) two-state system (qubit, spin) into the copy (C) and duplicate-copy
(D) two-state systems if the latter systems are initially in an arbitrary
state. We consider instead a quantum evolution in which the basis states of I
at time t are duplicated in at least two of the systems I, C, D, at time t +
Delta t. In essence, the restriction on the initial target states is exchanged
for uncertainty as to which two of the three qubits retain copies of the
initial source state.
