  We describe a design to implement a two-qubit geometric phase gate, by which
a pair of electrons confined in adjacent quantum dots are entangled. The
entanglement is a result of the Coulomb exchange interaction between the
optically excited exciton-polaritons and the localized spins. This optical
coupling, resembling the electron-electron Ruderman-Kittel-Kasuya-Yosida (RKKY)
inter- actions, offers high speed, high fidelity two-qubit gate operation with
moderate cavity quality factor Q. The errors due to the finite lifetime of the
polaritons can be minimized by optimizing the optical pulse parameters
(duration and energy). The proposed design, using electrostatic quantum dots,
maximizes entanglement and ensures scalability.
