Two-qubit state tomography with ensemble average in coupled superconducting qubits
Mengmeng Li, Guangming Xue, Xinsheng Tan, Qiang Liu, Kunzhe Dai, Ke Zhang, Haifeng Yu, Yang Yu · Applied Physics Letters · 2017
We propose a scheme to perform two-qubit state tomography by independently measuring the ensemble average of quantum states of two coupled superconducting transmon qubits. Each qubit is capacitively coupled to its own readout cavity and can be measured separately. In order to obtain the density matrix of a two-qubit state, we apply four two-qubit unitary operations to the initial state and measure the corresponding qubit states, from which the elements of the two-qubit density matrix can be extracted. By using this scheme, we measure the entangled two qubits with high fidelity.