Experimental demonstration of selective quantum process tomography on an NMR quantum information processor. (arXiv:1707.06739v2 [quant-ph] UPDATED)

We present the first NMR implementation of a scheme for selective and
efficient quantum process tomography without ancilla. We generalize this scheme
such that it can be implemented efficiently using only a set of measurements
involving product operators. The method allows us to estimate any element of
the quantum process matrix to a desired precision, provided a set of quantum
states can be prepared efficiently. Our modified technique requires fewer
experimental resources as compared to the standard implementation of selective
and efficient quantum process tomography, as it exploits the special nature of
NMR measurements to allow us to compute specific elements of the process matrix
by a restrictive set of sub-system measurements.To demonstrate the efficacy of
our scheme, we experimentally tomograph the processes corresponding to `no
operation', a controlled-NOT (CNOT), and a controlled-Hadamard gate on a
two-qubit NMR quantum information processor, with high fidelities.

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