QC-SQUARED · Accurate and efficient ab initio Quantum Chemistry calculations on current and near-term noisy intermediate-scale Quantum Computers for relevant chemical problems

Quantum computing has the potential to provide an exponential speedup compared to classical computers, but the practical implementation is still in its infancy.Two central questions are: (1) in which field the current noisy intermediate-scale quantum (NISQ) hardware can provide benefits compared to classical computers and (2) which methods and algorithms enable this advantage?The aim of this project is to answer these questions by enabling accurate and efficient Quantum Chemistry calculations on current and near-term Quantum Computers for relevant chemical and physical problems. This paves the road to simulate strongly correlated electron systems of high scientific and economical interest, where accurate approaches are needed to understand groundbreaking chemical and physical phenomena, like high-temperature superconductivity, photosynthesis or nitrogen fixation. It will be achieved by developing and implementing novel quantum algorithms based on the combination of the transcorrelated (TC) methodand a complete active space self-consistent field (CASSCF) embedding approach.The TC method will reduce the necessary quantum resources by providing accurate results for a small strongly correlated region already with small basis sets. While CASSCF will allow to target more realistic systems by embedding the correlated region self-consistently in a larger environment, which is efficiently described by inexpensive mean-field approaches.This project has the potential to go beyond the state-of-the-art by: (a) pushing the boundaries of currently possible quantum chemical calculations, allowing further theoretical understanding and practical design of quantum materials and (b) pave the road toward scientific and economical relevance of quantum computing already in the NISQ era.