Complete characterization of a multimode quantum black box
Ilya A. Fedorov, Aleksey K. Fedorov, Yury Kurochkin, Alexander I. Lvovsky · arXiv (Cornell University) · 2014
We develop a method of complete experimental characterization of an M-mode quantum optical process. By measuring its effect on coherent states via balanced homodyne tomography, we obtain the process tensor in the Fock basis. This rank-4M tensor, which predicts the effect of the process on an arbitrary density matrix, is iteratively reconstructed directly from the experimental data via the maximum-likelihood method. We demonstrate the capabilities of our method using the example of a beam splitter. In spite of purely classical nature of the measurement performed, we recover quantum properties of this optical element, in particular the Hong-Ou-Mandel effect.