Experimental demonstration of selective quantum process tomography on an NMR quantum information processor

TL;DR

This paper demonstrates a novel, resource-efficient method for quantum process tomography on an NMR quantum processor, enabling precise characterization of quantum gates with fewer measurements.

Contribution

It introduces a generalized, ancilla-free quantum process tomography scheme optimized for NMR systems, reducing experimental resources needed.

Findings

Successfully tomographed CNOT, controlled-Hadamard, and no-operation processes.

Achieved high-fidelity estimates of quantum processes.

Validated the efficiency and accuracy of the proposed method.

Abstract

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.