October 11, 2023

# Purdue researchers, IBM perform perturbation theory method on quantum computer

Professor Sabre Kais (image provided)

A recent study, led by Sabre Kais, Distinguished Professor of Chemistry and professor of electrical and computer engineering at Purdue University, and IBM’s Barbara Jones, used a quantum computer to perform chemical calculations via perturbation theory. The science could potentially be used to solve quantum mechanics problems on a larger scale using perturbation theory.

**Article Title**

Toward perturbation theory methods on a quantum computer

**Author(s)**

Barbara Jones, IBM Quantum

Sabre Kais, director, Center for Quantum Technologies; Distinguished Professor, Chemistry; professor, Electrical and Computer Engineering

Junxu Li, graduate student, Physics

**Journal**

Science Advances, 2023

**Full Article**

https://www.science.org/doi/10.1126/sciadv.adg4576

**Article Summary**

The Schrodinger equation, a generalization of the classical Newton’s equation of motion, is the fundamental equation of quantum mechanics that describes the world around us, particularly the structure and dynamics of molecules and materials. This equation can be solved exactly only for small molecular systems. With the current largest supercomputer, we can obtain an exact electronic structure of molecules with only 24 electrons. This limits us from obtaining accurate descriptions of possible outcomes of chemical reactions. However, quantum computing is widely expected to solve valuable problems that today’s computers cannot.

Perturbation theory is a useful systematic mathematical method to obtain an approximate solution to such an equation. It has been one of the most used methods for chemical calculations for over 50 years. With the recent advances in quantum computing algorithms, the question is how to implement perturbation methods on quantum devices.

In this study, led by Sabre Kais at Purdue University and Barbara Joes at IBM, researchers presented, for the first time, a general quantum circuit performing perturbation calculations and implemented the method on IBM’s quantum hardware.