Cooperative Enhancement of Optical Quantum Gates
J. D. Franson · Physical Review Letters · 1997
Nonlinear phase shifts at the two-photon level can be greatly enhanced by a cooperative effect involving pairs of atoms, which can give a phase shift proportional to the square of the number of atoms in a medium. This is a nonlocal quantum effect that does not exist for classical states of light. Cooperative effects of this kind may have practical applications in quantum computing.