[GS_C_QT]Variational Quantum Algorithms for Materials Science
ABSTRACT
The electron pair approximation offers an efficient variational quantum eigensolver (VQE) approach for electronic structure simulations on
quantum computers. With the number of entangling gates scaling quadratically with system size and a constant measurement overhead, the
orbital optimized unitary pair coupled cluster double (oo-upCCD) ansatz strikes a balance between accuracy and efficiency. However, the electron pair approximation prevents the method from achieving quantitative accuracy. To improve it, we explore the theory of second order perturbation (PT2) correction to oo-upCCD. For molecular bond stretching and chemical reactions, the method significantly improves the predicted energy accuracy, reducing oo-upCCD’s error by up to 90%. The predicted VQE-PT2 reaction energies are in excellent agreement with noise-free simulators after applying simple error mitigations solely on the VQE energies.
