Simple Experimental Evaluation of a Quantum Computer via Tomography and GHz States

This paper presents a simple experimental method for evaluating a superconducting quantum processor through two-qubit quantum state tomography and generalized GHZ-state benchmarking. The goal is to provide an accessible procedure for assessing hardware fidelity and entanglement capability. The method was demonstrated using IBM’s 127-qubit ibm_brisbane device, where each Bell state was prepared and reconstructed from 10,000 shots, and the resulting fidelities were compared to Qiskit Aer simulations. The method further examines multi-qubit GHZ states to gauge scalability. The main advantages are its simplicity, reproducibility on free IBM Quantum hardware, and its suitability for entry-level experimentation and performance evaluation.