Quantum Computation of Conical Intersections on a Programmable Superconducting Quantum Processor.

Area of Science:

• Quantum Chemistry
• Photochemistry
• Computational Science

Background:

• Conical intersections (CIs) are crucial for photochemical processes but computationally demanding for classical computers.
• Traditional methods struggle with the electronic Schrödinger equation in active spaces.
• Quantum computing presents a potential avenue for studying CIs, yet its practical application on real hardware is underexplored.

Purpose of the Study:

• To demonstrate the first hybrid quantum-classical state-average complete active space self-consistent field (VQE-SA-CASSCF) method on a superconducting quantum processor.
• To investigate conical intersections (CIs) in ethylene and triatomic hydrogen using this novel quantum approach.

Main Methods:

• Implementation of a hybrid quantum-classical VQE-SA-CASSCF algorithm.
• Execution on a superconducting quantum processor.
• Application to prototypical systems: ethylene (C2H4) and triatomic hydrogen (H3).

Main Results:

• Successful realization of VQE-SA-CASSCF on quantum hardware.
• Accurate description of conical intersections (CIs) in the studied systems.
• Demonstration of feasibility for current quantum devices with ongoing improvements.

Conclusions:

• The VQE-SA-CASSCF method is a viable approach for studying CIs on existing quantum hardware.
• This work paves the way for quantum computing's application to more complex photochemical systems.
• Advances in quantum hardware and algorithms will further enhance the capabilities for CI research.