Mapping Configuration Interaction Problems to a QuantumComputer

• Main Authors: Ting Tsai, 蔡霆
• Other Authors: 館希聖
• Format: Others
• Language: en_US
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/4t63pp

碩士 === 國立臺灣大學 === 物理學研究所 === 107 === The idea of using quantum computer to calculate the energies of molecules is came from Richard Feynman. In 1982, he mentioned “Nature isn’t classical, dammit, and if you want to make a simulation of nature, you’d better make it quantum mechanical, and by golly it’s a wonderful problem, because it doesn’t look so easy.” In 1996, Seth Lloyd used the quantum phase estimation algorithm (PEA) to calculate the ground state energy of a molecule. In theory, PEA is the most efficient method to solve this type of problems. However, the power of Noisy Intermediate Scale Quantum (NISQ) computer available in the next five to ten years is limited by error rate, noise, decoherent time, etc. Even for a small molecule, PEA is hard to implement effectively. Due to the breakthrough improvement on quantum devices made by IBM, how to make NISQ devices perform well becomes very important. Based on the limitation of NISQ devices, variational-quantum-eigensolver (VQE) is developed. In this thsis, we start from configuration interaction, discuss results with different encoding and optimization methods for the VQE to find elecreonic structure of molecules, and analyze pros and cons of the different methods.