Quantum Simulations of Fermionic Hamiltonians with Efficient Encoding and Ansatz Schemes

Area of Science:

• Quantum computing
• Computational physics
• Materials science

Background:

• Simulating fermionic Hamiltonians on quantum computers is challenging for complex spin defect systems.
• Conventional encodings and variational quantum eigensolver (VQE) methods have limitations in scalability and qubit requirements.

Purpose of the Study:

• To propose a novel computational protocol for quantum simulations of fermionic Hamiltonians.
• To enable feasible calculations on complex spin defect systems previously inaccessible.
• To improve the efficiency and noise resilience of quantum simulations for quantum technologies.

Main Methods:

• Utilizing a qubit-efficient encoding scheme to map Slater determinants onto qubits.
• Employing a modified qubit-coupled cluster ansatz.
• Integrating advanced noise-mitigation techniques.

Main Results:

• Achieved substantial improvements in the scaling of circuit gate counts and qubit numbers.
• Demonstrated a decrease in the number of required variational parameters, enhancing noise resilience.
• Successfully simulated complex spin defects, including the negatively charged silicon vacancy in 4H-SiC, for the first time.

Conclusions:

• The proposed protocol significantly advances the capability of quantum simulations for spin defect systems.
• This work paves the way for more accurate and efficient quantum technology development.
• The methodology is applicable to a range of spin defects relevant for quantum information science.