Quantum self-consistent equation-of-motion method for computing molecular excitation energies, ionization potentials,...

Area of Science:

• Quantum chemistry
• Computational materials science
• Quantum computing applications

Background:

• Accurate molecular simulations on quantum computers are key for material and chemical research.
• Current quantum devices can compute ground-state energies but struggle with excited states.
• Developing practical excited-state calculation methods for quantum devices is an active research area.

Purpose of the Study:

• To present a novel equation-of-motion-based method for computing molecular excitation energies on quantum computers.
• To adapt existing unitary coupled-cluster theory methods for quantum computation.
• To assess the performance and suitability of the new method for near-term quantum devices.

Main Methods:

• Developed a quantum self-consistent equation-of-motion (q-sc-EOM) method.
• Utilized the variational quantum eigensolver algorithm for ground-state calculations.
• Employed self-consistent operators to ensure vacuum annihilation conditions for accuracy.
• Performed numerical simulations on H2, H4, H2O, and LiH molecules.

Main Results:

• The q-sc-EOM method successfully computes excitation energies, ionization potentials, and electron affinities.
• Results show real and size-intensive energy differences, indicating accurate calculations.
• The method was tested against state-of-the-art techniques, demonstrating its viability.
• Numerical simulations confirmed the method's effectiveness for small molecules.

Conclusions:

• The q-sc-EOM method offers a reliable approach for excited-state calculations on quantum computers.
• It is particularly well-suited for Noisy Intermediate-Scale Quantum (NISQ) devices due to its expected noise resilience.
• This work advances the application of quantum computing in chemical and material research.