Low-Depth Unitary Coupled Cluster Theory for Quantum Computation.

Area of Science:

• Quantum computing
• Computational chemistry
• Electronic structure theory

Background:

• Unitary coupled cluster (UCC) is a promising method for quantum electronic structure calculations.
• Deep quantum circuits required by UCC for large systems pose implementation challenges.

Purpose of the Study:

• To develop a more efficient algorithm for UCC calculations on quantum computers.
• To reduce the depth of quantum circuits needed for electronic structure computations.

Main Methods:

• Devised an algorithm using Taylor expansion in small amplitudes of UCC.
• Traded circuit depth for additional quantum measurements.
• Incorporated strong correlations by expanding about a small set of exact UCC factors.

Main Results:

• The Taylor expansion approach effectively reduces circuit depth.
• The method remains accurate for both weakly and strongly correlated molecules.
• Only a few UCC factors require exact treatment as molecular correlations increase.

Conclusions:

• The proposed algorithm offers a practical solution for deep UCC circuits in quantum computations.
• This method enhances the feasibility of accurate electronic structure calculations on current quantum hardware.
• It provides a scalable approach for studying molecular systems with varying correlation strengths.