Full Characterization of Genuine 17-qubit Entanglement on the Superconducting Processor

Area of Science:

• Quantum Information Science
• Quantum Computing
• Quantum State Estimation

Background:

• Quantum state tomography (QST) is crucial for characterizing quantum systems.
• Entanglement verification is essential for quantum information processing.
• Accurate state estimation in noisy quantum systems remains a challenge.

Purpose of the Study:

• To present a novel least-square state estimator regularized by state purity.
• To achieve scalable full-state quantum state tomography.
• To verify genuine multiqubit entanglement in quantum states.

Main Methods:

• Utilized a least-square state estimator with state purity regularization.
• Performed experimental validation on a superconducting quantum processor.
• Employed entanglement witnesses for verification.

Main Results:

• Achieved high state fidelity for 9-qubit W states (0.8217) and 17-qubit Greenberger-Horne-Zeilinger states (0.6817).
• Demonstrated superior tomography accuracy with limited measurement settings.
• Conclusively certified genuine multiqubit entanglement in generated states.

Conclusions:

• The developed method enables accurate full characterization of many-body quantum systems.
• Error mitigation is crucial for utilizing noisy quantum systems effectively.
• This work paves the way for characterizing larger-scale quantum systems.