Quantum process tomography of two-qubit controlled-Z and controlled-NOT gates using superconducting phase qubits
Tsuyoshi Yamamoto, M. Neeley, Erik A. Lucero, Radoslaw C. Bialczak, J. Kelly, M. Lenander, M. Mariantoni, A. D. O’Connell, D. Sank, H. Wang, Martin P. Weides, J. Wenner, Yi Yin, Andrew N. Cleland, John M. Martinis · Physical Review B · 2010
We experimentally demonstrate quantum process tomography of controlled-Z and controlled-NOT gates using capacitively coupled superconducting phase qubits. These gates are realized by using the $|2⟩$ state of the phase qubit. We obtain a process fidelity of 0.70 for the controlled phase and 0.56 for the controlled-NOT gate, with the loss of fidelity mostly due to single-qubit decoherence. The controlled-Z gate is also used to demonstrate a two-qubit Deutsch-Jozsa algorithm with a single function query.