Quantum Equation of Motion with Orbital Optimization for Computing Molecular Properties in Near-Term Quantum...

Area of Science:

• Quantum computing applications in chemistry and materials science.
• Development of quantum algorithms for molecular property determination.

Background:

• Quantum computing offers a powerful approach for determining molecular and material properties.
• A key challenge is utilizing noisy, near-term quantum computers for practical problems.

Purpose of the Study:

• To present a novel quantum algorithm, oo-VQE-qEOM, for calculating molecular properties.
• To leverage variants of the quantum equation-of-motion (qEOM) and orbital-optimized variational quantum eigensolver (oo-VQE).

Main Methods:

• Developed the oo-VQE-qEOM quantum algorithm for computing expectation values.
• Performed noise-free quantum simulations for BeH2, H4, and H2O molecules.
• Utilized an active space of four electrons and four spatial orbitals (8 qubits).

Main Results:

• Calculated excitation energies, electronic absorption, and circular dichroism spectra.
• Successfully simulated molecular properties for BeH2, H4, and H2O across different basis sets.
• Demonstrated the algorithm's ability to match classical CASSCF calculation results.

Conclusions:

• The oo-VQE-qEOM algorithm is effective for calculating molecular properties on quantum computers.
• The approach shows promise for practical applications in quantum chemistry.
• Validated the algorithm against established classical computational chemistry methods.