Recorded 30 March 2022. Laura Gagliardi of the University of Chicago presents "Localized-Wave-Function Methods in Quantum Chemistry and Their Extension to Quantum Computers" at IPAM's Multiscale Approaches in Quantum Mechanics Workshop. Abstract: Quantum chemistry calculations of large, strongly correlated systems based on multireference wave functions are typically limited by the computation cost that scales exponentially with the size of the active space used to describe the phenomena of interest. One way to reduce the cost is to use fragmentation methods. The localized active-space self-consistent field (LASSCF) method [1] is an example of such a strategy. LASSCF is designed for applications in which electrons are strongly correlated in different weakly interacting physical regions of a molecule and approximates the strongly correlated part of the wave function as a single anti-symmetrized product of subspace wave functions. The computational cost of LASSCF is a linear function of the number of such unentangled subspaces. In this lecture I will give an overview of LASSCF and other localization methods and I will describe a framework for quantum algorithms, inspired by classical LASSCF. The wave function within a fragment is solved by using the quantum phase estimation (QPE) algorithm, and correlation between fragments is encoded variationally by using an ansatz that entangles the fragments. This approach [2] goes beyond what can be achieved with classical fragment methods, by providing additional correlation between fragments, while significantly reducing the total computational time compared with full QPE. [1] M. R. Hermes, R. Pandharkar, and L. Gagliardi, J. Chem. Theory Comput. 16, 4923 (2020). [2] M. Otten, M. R. Hermes, R. Pandharkar, Y. Alexeev, S. K. Gray, L. Gagliardi 10.26434/chemrxiv-2021-0nmwt (2021) Learn more online at: http://www.ipam.ucla.edu/programs/workshops/workshop-i-multiscale-approaches-in-quantum-mechanics/?tab=schedule