Realization of quantum process tomography in NMR

Quantum process tomography (QPT) was used to characterize the dynamics of a two-qubit nuclear magnetic resonance (NMR) quantum computer. The fidelity of a controlled-NOT logic gate and validity of an independent error model were studied to analyze quantum error correction and fault-tolerant computation. The covariance matrix of phase shifts was used to define the amount of damping and the extent of correlation. Analysis suggested that imperfect pulse calibration and inhomogeneity of radio frequency (rf) fields associated with process tomography were the primary sources of error.