Multiple Quantum Coherence Verification: Characterizing Entanglement Noise in Superconducting Quantum Processors

Quantum processors based on superconducting circuits are promising candidates for scalable quantum computing, yet they are susceptible to specific noise types that degrade entanglement fidelity. This study presents a novel approach using the Greenberger-Horne-Zeilinger (GHZ) verification protocol to characterize source noise affecting these processors' entangling gates. Our method focuses on detecting depolarization errors and crosstalk effects, predominant noise channels that often go unnoticed yet significantly impact quantum gate performance. To enhance the detection sensitivity of our protocol, we employ a hidden inverse technique aimed at mitigating coherent errors, complemented by unitary folding to amplify incoherent effects, thus providing a more nuanced noise profile. Our approach requires minimal experimental resources, making it a practical choice for routine noise characterization in multi-qubit systems. We validate our methodology through rigorous theoretical analysis, simulations, and on-hardware experiments conducted on IBM quantum devices. The results demonstrate notable accuracy in noise characterization, with implications for optimizing quantum error correction codes and enhancing overall quantum circuit fidelity. Our findings underscore the necessity for tailored noise-mitigation strategies to pursue fault-tolerant quantum computing. This work marks a step forward in the practical realization of more reliable quantum computations, particularly for applications demanding high-precision quantum control.