title: Selective and efficient quantum process tomography with single photons.
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)10.1103/PhysRevLett.100.190403]} 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.
authors.affiliation: Departamento de Física and IFIBA, FCEyN, UBA, Pabellón 1, Ciudad Universitaria, 1428 Buenos Aires, Argentina.
authors.forename: Christian Tomás
authors.initials: CT
authors.lastname: Schmiegelow
authors.forename: Miguel Antonio
authors.initials: MA
authors.lastname: Larotonda
authors.forename: Juan Pablo
authors.initials: JP
authors.lastname: Paz