  In-plane, inter-carrier correlations in hole doped cuprates are investigated
by ab initio multiconfiguration calculations. The dressed carriers display
features that are reminiscent of both Zhang-Rice (ZR) CuO4 singlet states and
Jahn-Teller polarons. The interaction between these quasiparticles is
repulsive. At doping levels that are high enough, the interplay between
long-range unscreened Coulomb interactions and long-range phase coherence among
the O-ion half-breathing vibrations on the ZR plaquettes may lead to a strong
reduction of the effective adiabatic energy barrier associated to each
polaronic state. Tunneling effects cannot be neglected for a relatively flat,
multi-well energy landscape. We suggest that the coherent, superconducting
quantum state is the result of such coherent quantum lattice fluctuations
involving the in-plane O ions. Our findings appear to support models where the
superconductivity is related to a lowering of the in-plane kinetic energy.
