Size-Consistent Quantum Chemistry on Quantum Computers.

Area of Science:

• Quantum Computing
• Computational Chemistry
• Materials Science

Background:

• Hybrid quantum-classical algorithms utilize quantum devices for molecular simulations.
• Scalable quantum chemistry requires size consistency, where energies of non-interacting subsystems scale linearly.
• Quantum hardware noise can degrade size consistency by coupling independent subsystems.

Purpose of the Study:

• To systematically evaluate the size consistency of quantum hardware for molecular simulations.
• To assess the impact of quantum device noise on a fundamental property of quantum chemistry.
• To demonstrate the feasibility of noise-resilient quantum simulations for strongly correlated systems.

Main Methods:

• Simulated systems of increasing numbers of non-interacting H2 molecules on quantum hardware.
• Employed optimally shallow unitary circuits for efficient quantum computations.
• Evaluated size consistency by analyzing molecular energies across different system sizes.

Main Results:

• Molecular energies remained size-consistent within chemical accuracy for up to 118 H2 subsystems (one-qubit unitary) and 71 H2 subsystems (two-qubit unitary).
• Demonstrated that current quantum devices preserve size consistency over chemically relevant system sizes.
• Indicated that quantum hardware noise does not significantly degrade size consistency for these simulations.

Conclusions:

• Current quantum hardware can maintain size consistency for molecular simulations, a crucial property for quantum chemistry.
• The findings support the feasibility of scalable and noise-resilient quantum simulations for complex molecules and materials.
• This work paves the way for advanced quantum simulations in chemistry and materials science.