The problem of preparing entangled pairs of polarization qubits in the frequency-nondegenerate regime

摘要

The problems associated with the practical implementation of the scheme proposed for preparation of arbitrary states of polarization ququarts based on biphotons have been discussed. The influence of effects of frequency dispersion are considered, and the necessity of compensating the dispersion of group velocities in the frequency-nondegenerate case even for continuous pumping is demonstrated. A method for this compensation is proposed and implemented experimentally. Physical restrictions on the quality of the prepared two-photon states are revealed.