Correction Scheme for Molecular Total Energies From Quantum Phase Estimation Under Limited Qubit Resources

Area of Science:

• Quantum computing
• Computational chemistry
• Molecular modeling

Background:

• Accurate calculation of molecular total energies is crucial for understanding chemical reactions and properties.
• Current computational methods face challenges with scalability for large molecular systems.
• Integrating quantum and classical computing offers a promising avenue for enhanced computational power.

Purpose of the Study:

• To develop a practical and accurate hybrid quantum-classical method for evaluating molecular total energies.
• To enable the treatment of larger molecular systems by combining limited quantum and classical resources.
• To demonstrate the effectiveness of the proposed scheme in post-correcting quantum-derived energies.

Main Methods:

• The proposed scheme integrates fault-tolerant quantum computers with classical computing.
• Quantum Dominant Orbital Selection (QDOS) extracts essential active orbitals for a compact active space.
• Subspace Dynamical Correlation (SDC) evaluates dynamical-correlation corrections on classical machines.

Main Results:

• QDOS yields a compact active space suitable for classical Complete Active Space Configuration Interaction (CASCI) calculations.
• SDC effectively post-corrects CASCI energies obtained from quantum computations.
• The hybrid approach was examined within multireference perturbation theory and tailored coupled-cluster theory frameworks.

Conclusions:

• The developed hybrid method offers an accurate and practical approach for molecular total energy evaluation.
• This scheme effectively combines limited quantum and classical resources for analyzing larger molecular systems.
• The integration of QDOS and SDC provides a scalable pathway for advanced computational chemistry.