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Updated: Jun 2, 2025

Generation and Coherent Control of Pulsed Quantum Frequency Combs
Published on: June 8, 2018
FCIQMC-CASPT2 with Imaginary-Time-Averaged Wave Functions
Arta A Safari1, Robert J Anderson1, Ali Alavi1,2
1Max-Planck-Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany.
Abstract:
A new method to perform complete active space second-order perturbation theory on top of large active spaces optimized with full configuration quantum Monte Carlo is presented. Computing the three- and Fock-contracted four-particle density matrix from imaginary-time-averaged wave functions is found to resolve fermionic positivity violations and to ensure numerical stability. The protocol is applied to [NiFe]-hydrogenase, [Cu2O2]-oxidase and Fe-porphyrin model systems up to 26 electrons in 27 orbitals and benchmarked against DMRG-CASPT2.
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