QLunch: Jakob Günther

Speaker: Jakob Günther from QMATH

Title: More Quantum Chemistry with Fewer Qubits

Abstract: Quantum computing is a promising paradigm for electronic structure simulation of physical and chemical systems, a problem which is hard to solve classically. Of particular interest for chemistry is the calculation of the electronic ground state energy, a quantity that lies at the heart of quantum chemistry. State-of-the-art quantum algorithms can simulate a reduced-dimensional representation of the molecular electronic problem and, under reasonable assumptions, compute the ground state energy efficiently. However, improving the reduced-dimensional representation with standard quantum algorithms comes at the cost of higher qubit counts. Before this background, we developed a quantum algorithm that improves on the physical representation via perturbation theory, without increasing the number of qubits.

 In this talk I will introduce key concepts of quantum chemistry and explain how a reduced-dimensional representation of the molecular electronic structure problem can be mapped to a (digital) quantum computer. Furthermore, I will present a quantum algorithm for computing first and second order perturbation theory energy corrections and show how this applies to multireference perturbation theory (MRPT). 

Based on joint work with Alberto Baiardi, Markus Reiher and Matthias Christandl (arXiv:2308.16873).