Selective and Efficient Quantum Process Tomography with Single Photons.

CHRISTIAN SCHMIEGELOW

Mexico DF

Simposio; Encuentro Rio-Mexico de Optica Cuántica; 2010

UNAM

We present experimental results demonstrating a photonic implementation of an efficient quantum algorithm that estimates any parameter characterizing an arbitrary quantum process. The algorithm, introduced first in [PRL100,190403(2008)] not only enables estimation of selected parameters using polynomial resources but also can be used to efficiently determine all the elements of the $chi$--matrix that are larger than a fixed value. In our laboratory we performed full and partial quantum process tomography on a channel affecting the qubit encoded in the polarization of single photons[PRL104,123601(2010)]. Here, we report new results for the quantum process tomography on a channel affecting two qubits, encoded in the polarization and the path degrees of freedom of single photons generated by parametric down conversion. We compare our results with the ones obtained using standard quantum process tomography showing that for the two--qubit channel the new selective method is already more efficient than the standard one.