We report that a recent active space model of the nitrogenase FeMo cofactor, proposed in the context of quantum simulations, is not representative of the electronic structure of the FeMo cofactor ground-state. Although quantum resource estimates, outside of the cost of adiabatic state preparation, will not be much affected, conclusions should not be drawn from the complexity of classical simulations of the electronic structure of this system in this active space. We provide a different model active space for the FeMo cofactor that contains the basic open-shell qualitative character, which may be useful as a benchmark system for making classical and quantum resource estimates.

We develop a versatile master equation approach to describe the nonequilibrium dynamics of a two-level system in contact with a bosonic environment, which allows for the exploration of a wide range of parameter regimes within a single formalism. As an experimentally relevant example, we apply this technique to the study of excitonic Rabi rotations in a driven quantum dot, and compare its predictions to the numerical Feynman integral approach. We find excellent agreement between the two methods across a generally difficult range of parameters. In particular, the variational master equation technique captures effects usually considered to be nonperturbative, such as multiphonon processes and bath-induced driving renormalization, and can give reliable results even in regimes in which previous master equation approaches fail.

Extensions of the recently introduced "Morse/long-range" (MLR) potential function form allow a straightforward treatment of a molecular state for which the inverse-power long-range potential changes character with internuclear separation. Use of this function in a direct-potential-fit analysis of a combination of new fluorescence data for (7,7)Li(2), (6,6)Li(2), and (6,7)Li(2) with previously reported data for the A((1)Sigma(u) (+)) and X((1)Sigma(g) (+)) states yields accurate, fully analytic potentials for both states, together with the analytic "adiabatic" Born-Oppenheimer breakdown radial correction functions which are responsible for the difference between the interaction potentials and well depths for the different isotopologues. This analysis yields accurate well depths of D(e)=8516.709(+/-0.004) and 8516.774(+/-0.004) cm(-1) and scattering lengths of 18.11(+/-0.05) and 23.84(+/-0.05) A for the ground-states of (7,7)Li(2) and (6,6)Li(2), respectively, as well as improved atomic radiative lifetimes of tau(2p)=27.1018(+/-0.0014) ns for (7)Li(2p) and 27.1024(+/-0.0014) ns for (6)Li(2p).