Photonic time-bin qubit generation with a tripod atomic system
Davit Aghamalyan, Yu. P. Malakyan · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2010
A new method of preparing a single photon in temporally delocalized entangled modes is proposed and analyzed. We show that in a medium of four-level atoms with tripod-level configuration a strong parametric interaction between two one-photon pulses emerges, if the medium was initially prepared in a coherent superposition of the two ground states, while a strong classical field drives the neighbor transition from the third ground state. The analytical solution of Maxwell equations reveals that under the electromagnetically induced transparency (EIT), the quantum fields propagate with significantly small absorption and with different group velocities that leads to their temporal split into well-separated pulses, the amplitudes of which are well controlled by the driving field. The proposed scheme can serve as a robust source of narrow-band one-photon qubits with an entanglement between two temporal modes, not sensitive to losses in atmosphere and in telecommunication waveguides. We show also that in our scheme a controllable degree of temporal entanglement can be achieved.