Partial tomography, which focuses on reconstructing reduced density matrices (RDMs), has emerged as a promising approach for characterizing complex quantum systems, particularly when full state tomography is impractical. Recently, overlapping tomography has been proposed as an efficient method for determining all $k$-qubit RDMs using logarithmic polynomial measurements, though it has not yet reached the ultimate limit. Here, we introduce a unified framework for optimal quantum overlapping tomography by mapping the problem to the clique cover model. This framework provides the most efficient and experimentally feasible measurement schemes to date, significantly reducing the measurement costs. Our approach is also applicable to determining RDMs with different topological structures. Moreover, we experimentally validate the feasibility of our schemes on a practical nuclear-spin processor using average measurements, and further apply our method to noisy data from superconducting quantum processors employing projection measurements. The results validate the utility of overlapping tomography, paving the way for the characterization of advanced quantum systems and learning about state properties in the future.

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• Optimization problems
• Quantum information processing
• Quantum measurements
• Quantum protocols
• Quantum tomography
• Density matrix methods
• Graph theory