Polarization states of four-dimensional systems based on biphotons
Yu. I. Bogdanov, Ekaterina Moreva, Gleb Maslennikov, R. F. Galeev, Stanislav S. Straupe, S. P. Kulik · Physical Review A · 2006
We discuss the concept of polarization states of four-dimensional quantum systems based on the frequency nondegenerate biphoton field. Several quantum tomography protocols were developed and implemented for the measurement of an arbitrary state of ququart. A simple method that does not rely on the interferometric technique is used to generate and measure the sequence of states that can be used for quantum communication purposes.