State Tomography of Superconducting Multi-Qubits in Circuit QED

Abstract

It is a challenge to identify the quantum state with high fidelity as the quantum system size becomes large. The larger system size requires more parameters to be calculated and hence more measurement and more time. For example, 16 and 64 parameters are needed to express two and three qubit state in density matrix, respectively. Here each parameter is determined by the quantum state tomography (QST) after the initial state is prepared by performing simple single gate operations and/or two qubit CNOT gate. This enables us to determine the state fidelity of the given state preparation.