Demonstrating a Continuous Set of Two-Qubit Gates for Near-Term Quantum Algorithms

Area of Science:

• Quantum computing
• Quantum algorithms
• Quantum hardware optimization

Background:

• Quantum algorithms promise significant speedups for computational chemistry and material science.
• Near-term quantum algorithms require optimization for noisy, resource-limited quantum hardware.

Purpose of the Study:

• To demonstrate a continuous two-qubit gate set optimized for existing noisy quantum hardware.
• To reduce circuit depth for quantum simulations.

Main Methods:

• Utilized adjustable coupling of gmon qubits.
• Implemented continuous imaginary swap-like (iSWAP-like) and controlled-phase gate families.
• Benchmarked gate fidelity across the fSim(θ,ϕ) parameter space.

Main Results:

• Achieved a threefold reduction in circuit depth compared to standard decompositions.
• Demonstrated an arbitrary two-qubit gate within the excitation-preserving subspace.
• Attained a purity-limited average two-qubit Pauli error of 3.8×10⁻³ per fSim gate.

Conclusions:

• The developed gate set enables efficient implementation of the Fermionic simulation (fSim) gate set on current quantum devices.
• This optimization is crucial for advancing quantum simulations in chemistry and material science.
• The results highlight the potential of tunable couplers for near-term quantum computing applications.