The two-electron reduced-density matrix (2-RDM) contains enough information to exactly represent the electronic energy of an atom or molecule within a given basis set, suggesting that the 2-RDM could be used in place of the N-electron wave function as the central variable in quantum chemistry.  However, the variational optimization of the energy with respect to the elements of the 2-RDM must be performed subject to a set of constraints to guarantee that the 2-RDM corresponds to a realistic N-electron wave function.   The determination of ground state energies using variational 2-RDM methods is well understood and has become quite common.  Somewhat less common are accurate descriptions of excited states based on the 2-RDM, despite the fact that the 2-RDM should contain enough information to describe them.  We demonstrate that accurate excited-state energies can be extracted from a real-time time-dependent formulation of the usual ground-state variational 2-RDM method.  Our preliminary results suggest that one can accurately describe the interaction of shaped optical pulses with electrons in systems with multireference character without the use of the N-electron wave function.

Extracting excited states from a real-time time-dependent variational 2-RDM theory

248th National Meeting (2014)

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