How to measure a molecule’s energy using a quantum computer

Simulating molecules on quantum computers just got much easier with IBM’s superconducting quantum hardware. In a recent research article published in Nature, Hardware-efficient Variational Quantum Eigensolver for Small Molecules and Quantum Magnets, we implement a new quantum algorithm capable of efficiently computing the lowest energy state of small molecules. By mapping the electronic structure of molecular orbitals onto a subset of our purpose-built seven qubit quantum processor, we studied molecules previously unexplored with quantum computers, including lithium hydride (LiH) and beryllium hydride (BeH2). The particular encoding from orbitals to qubits studied in this work can be used to simplify simulations of even larger molecule and we expect the opportunity to explore such larger simulations in the future, when the quantum computational power (or “quantum volume”) of IBM Q systems has increased.