Selective and efficient quantum process tomography with single photons

TL;DR

This paper demonstrates a photonic implementation of an efficient quantum process tomography method that estimates quantum channels with resources scaling polynomially, using single photons and 2-design sampling.

Contribution

It provides the first experimental realization of a polynomial-resource quantum process tomography method using single photons.

Findings

Successfully implemented the method on polarization qubits.

Compared the new method with existing techniques, highlighting advantages.

Achieved efficient estimation of quantum process elements with fewer resources.

Abstract

We present the results of the first photonic implementation of a new method for quantum process tomography. The method (originally presented by A. Bendersky et al, Phys. Rev. Lett 100, 190403 (2008)) enables the estimation of any element of the chi-matrix that characterizes a quantum process using resources that scale polynomially with the number of qubits. It is based on the idea of mapping the estimation of any chi-matrix element onto the average fidelity of a quantum channel and estimating the latter by sampling randomly over a special set of states called a 2-design. With a heralded single photon source we fully implement such algorithm and perform process tomography on a number of channels affecting the polarization qubit. The method is compared with other existing ones and its advantages are discussed.