7.2. Quantum chemistry

In Chapter 4, Molecular Hamiltonians and Chapter 5, Variational Quantum Eigensolver (VQE) Algorithm, we illustrated some of the methods of quantum computational chemistry with Python and open-source quantum chemistry packages PySCF, ASE, PyQMC, and Qiskit, solving for the ground state energy level and plotting the BOPES of the hydrogen molecule, the lithium hydride molecule, and the macro-molecule ONCHHC. With the simplest basis (STO-3G), and with a noise-free simulation of a quantum circuit (statevector simulator), the different methods of calculations were in good agreement.

Scientific or industrial applications require highly accurate relative energy estimates of about 1 milli-Hartree (mHA) or even 0.1 mHA of chemical reaction mechanisms. The same accuracy is required for the total electronic energy of each molecule species involved in a chemical reaction of interest [Burg]. The authors of a benchmark of algorithms for calculating the electronic structures...