Analytical Nonadiabatic Couplings and Gradients within the State-Averaged Orbital-Optimized Variational Quantum...

Area of Science:

• Quantum computing
• Computational chemistry
• Quantum algorithms

Background:

• Current quantum computers have limitations for complex molecular simulations.
• The state-averaged orbital-optimized variational quantum eigensolver (SA-OO-VQE) is a recent algorithm for quantum chemistry.
• Efficiently resolving individual eigenstates and calculating analytical gradients are critical challenges.

Purpose of the Study:

• To introduce technical and analytical extensions to the SA-OO-VQE algorithm.
• To enable efficient state-resolution and analytical gradient estimation within the equi-ensemble framework.
• To demonstrate the accuracy and applicability of the enhanced algorithm on a relevant molecular system.

Main Methods:

• Developed an efficient state-resolution procedure for SA-OO-VQE.
• Implemented a method for estimating analytical gradients and nonadiabatic couplings.
• Applied the extended SA-OO-VQE to the formaldimine (CH2NH) molecule.

Main Results:

• The new state-resolution method avoids expensive intermediate calculations.
• Analytical gradients and nonadiabatic couplings are accurately estimated.
• Geometry optimization successfully located a conical intersection in formaldimine.

Conclusions:

• The extended SA-OO-VQE algorithm overcomes limitations of current quantum hardware.
• The enhancements are crucial for simulating quantum dynamics and locating conical intersections.
• This work advances the application of quantum algorithms in computational chemistry and molecular dynamics.