Consistency test for quantum process tomography

Sabine Wölk, Theeraphot Sriarunothai, Gouri S. Giri, Christof Wunderlich

Published 2018-08-30Version 1

It is generally assumed that every process in quantum physics can be described mathematically by a completely positive map. However, experimentally reconstructed processes are not necessar- ily completely positive due to statistical or systematic errors. In this paper, we introduce a test for discriminating statistical from systematic errors which is necessary to interpret experimentally reconstructed, non-completely positive maps. We demonstrate the significance of the test using several examples given by experiments and simulations. In particular, we demonstrate experimen- tally how an initial correlation between the system to be measured and its environment leads to an experimentally reconstructed map with negative eigenvalues. These experiments are carried out using atomic 171 Yb+ ions confined in a linear Paul trap, addressed and coherently manipulated by radio frequency radiation.