Consistent-histories and dipolar-basis representation of nonlinear response functions - art. no. 021804

By expanding optical response functions in the eigenstates of the dipole op erator (rather than of the Hamiltonian), we obtain a path-integral represen tation that lends itself more readily to classical simulations. Connection is made to stochastic (consistent-histories) theories of quantum dynamics o f single quantum systems by computing the entire probability distribution o f the observed polarization (rather than merely its expectation value). The weight of each Liouville space path contributing to Be optical response is complex, and cannot be recast using the joint probabilities used in the co nsistent-histories approach.