  It is strong Coulomb effects in carbon nanotubes that lead to formation of
the so-called "bright" and "dark" (forbidden one-photon optical transition)
exciton states, and dramatically decrease the efficiency of one-photon light
emission via trapping of the carriers by "dark" states. We demonstrate that the
proper use of these "bright" and "dark" exciton states with distinctively
different recombination times may turn the situation around: the use of quantum
coherence and multiphoton schemes of excitation potentially not only allow one
to efficiently manipulate the dark states, but can also create conditions for
efficient light generation in different frequency regions, produce "slow" or
"fast" light, implement quantum light storage, media with a negative refractive
index, and other quantum-optical regimes. Possible quantum-optical carbon
nanotube devices have a potential for suitable performance at elevated
temperatures, because the binding energies of excitons in single-walled
nanotubes are hundreds-of-meV high.
