  We investigated kinetic properties of correlated pairing states in strongly
correlated phase of the Hubbard model in two space dimensions. We employ an
optimization variational Monte Carlo method, where we use the improved wave
function $\psi_{\lambda}= e^{-\lambda K}\psi_G$ for the Gutzwiller wave
function $\psi_G$ with $K$ being the kinetic part of the Hamiltonian. The
Gutzwiller-BCS state is stabilized as the potential energy driven
superconductivity because the Coulomb interaction energy is lowered while the
kinetic energy increases in this state. In contrast, we show that in the
$\psi_{\lambda}$-BCS wave function $\psi_{\lambda-BCS}= e^{-\lambda
K}P_G\psi_{BCS}$, the Coulomb energy increases and instead the kinetic energy
is lowered in the strongly correlated phase where the Coulomb repulsive
interaction $U$ is large. The correlated superconducting state is realized as a
kinetic energy driven pairing state and this indicates the enhancement of
superconductivity due to kinetic-energy effect.
