Complete characterization of the directly implementable quantum gates
  used in the IBM quantum processors
Quantum process tomography of each directly implementable quantum gate used
in the IBM quantum processors is performed to compute gate error in order to
check viability of complex quantum operations in the superconductivity-based
quantum computers introduced by IBM and to compare the quality of these gates
with the corresponding gates implemented using other technologies. Quantum
process tomography (QPT) of C-NOT gates have been performed for three
configurations available in IBM QX4 processor. For all the other allowed gates
QPT have been performed for every allowed position (i.e., by placing the gates
in different qubit lines) for IBM QX4 architecture, and thus, gate fidelities
are obtained for both single-qubit and 2-qubit gates. Gate fidelities are
observed to be lower than the corresponding values obtained in the other
technologies, like NMR. Further, gate fidelities for all the single-qubit gates
are obtained for IBM QX2 architecture by placing the gates in the third qubit
line ($q[2]$). It's observed that the IBM QX4 architecture yields better gate
fidelity compared to IBM QX2 in all cases except the case of $\operatorname{Y}$
gate as far as the gate fidelity corresponding to the third qubit line is
concerned. In general, the analysis performed here leads to a conclusion that a
considerable technological improvement would be inevitable to achieve the
desired scalability required for the realization of complex quantum operations.
Abhishek Shukla Mitali Sisodia Anirban Pathak