  We propose a molecular setup for the physical implementation of a barrier
global quantum computation scheme based on the electron-doped pi-conjugated
copolymer architecture of nine blocks PPP-PDA-PPP-PA-(CCH-acene)-PA-PPP-PDA-PPP
(where each block is an oligomer). The physical carriers of information are
electrons coupled through the Coulomb interaction, and the building block of
the computing architecture is composed by three adjacent qubit systems in a
quasi-linear arrangement, each of them allowing qubit storage, but with the
central qubit exhibiting a third accessible state of electronic energy far away
from that of the qubits' transition energy. The third state is reached from one
of the computational states by means of an on-resonance coherent laser field,
and acts as a barrier mechanism for the direct control of qubit entanglement.
Initial estimations of the spontaneous emission decay rates associated to the
energy level structure allow us to compute a damping rate of order 10^{-7} s,
which suggest a not so strong coupling to the environment. Our results offer an
all-optical, scalable, proposal for global quantum computing based on
semiconducting pi-conjugated polymers.
