A Stabilizer Framework for the Contextual Subspace Variational Quantum Eigensolver and the Noncontextual Projection...

Area of Science:

• Quantum Computing
• Computational Chemistry
• Quantum Algorithms

Background:

• Noisy Intermediate-Scale Quantum (NISQ) devices show promise for quantum chemistry applications.
• Current quantum computers struggle with scientifically significant problems due to algorithmic limitations.
• Variational Quantum Eigensolver (VQE) is a key algorithm for NISQ devices.

Purpose of the Study:

• To address challenges in implementing Contextual Subspace Variational Quantum Eigensolver (CS-VQE) on NISQ devices.
• To develop an effective ansatz strategy for CS-VQE by addressing Hamiltonian partitioning.
• To enable precise ground state energy calculations for molecules using quantum computers.

Main Methods:

• Partitioning the molecular Hamiltonian into noncontextual (classical) and contextual (quantum) components.
• Developing a "noncontextual projection" ansatz strategy for CS-VQE.
• Reformulating CS-VQE within the stabilizer formalism for ansatz restriction.
• Utilizing quantum simulators for validation.

Main Results:

• Demonstrated a novel ansatz approach for CS-VQE compatible with NISQ devices.
• Achieved chemically precise ground state energy calculations for small molecules.
• Significantly reduced qubit count and circuit depth requirements.

Conclusions:

• The proposed noncontextual projection ansatz facilitates practical CS-VQE implementation on NISQ hardware.
• This method enhances the feasibility of using quantum computers for accurate molecular energy calculations.
• The approach offers a pathway to leverage NISQ devices for real-world scientific problems in chemistry.