Multiscale Electronic Structure Calculations via Projection Based Quantum Embedding*

Simulation of matter at the molecular scale on quantum computers has been restricted by the limitations of current hardware. As a result, only small chemical systems - such as H₂ - have been studied to date. To move calculations towards more complex molecular systems, we propose utilizing a projection based embedding theory. This allows an electronic structure problem to be split into conventional density functional theory calculations and a wave function problem. We propose solving the latter on a quantum device and the remainder using conventional computers. As there is freedom to choose the size of the quantum problem, we show how this embedding procedure can generate molecular Hamiltonians requiring fewer quantum resources to simulate.