High-intensity pulsed source of space-time and polarization double-entangled photon pairs - art. no. 011802

Two spatially separated type-I nonlinear crystals are pumped by femtosecond laser pulses to create entangled photon pairs in the process of spontaneou s parametric down-conversion. The two-photon entangled state exhibits high- visibility quantum interference for both polarization and space-time variab les without the need of stringent spectral postselection by using narrow-ba nd filters. The visibility is insensitive to the thickness of the crystals, unlike in the case of pulse pumped type-II parametric down-conversion; the refore the intensity can be easily increased by using thick nonlinear cryst als. This method will be indispensable in experiments that require a pulsed source of entangled photon pairs, such as generation of multiphoton entang led states, quantum teleportation, and quantum communications.