Objective #2
Sources of Entangled Photons

Multipartite entanglement with N>2 suitable for quantum applications is difficult to achieve because of the low efficiency of cascaded spontaneous down conversion. The production rates for such multiphoton states range from 200 mHz for 4 photon states down to 2.5 mHz for 8 photon states. SUPERTWIN's ambition is to build electrically pumped N-partite entangled photon source with high rate of quantum state production. We expect to experimentally confirm N=5 photon entanglement with the production rate 1 kHz (5 photon coincidence rate).

The SUPERTWIN Consortium will build a handy solid state sources of highly entangled photon states utilizing cooperative effect of Dicke superradiance emission in epitaxial heterostructures based on group-III nitride and III-V alloys for respective emissions at 400nm and 780nm.

The feasibility of this objective is inspired, on one side, by recent progress in reaching superradiance (or superfluorescence) in various quantum-confined semiconductor heterostructure systems. These ranges from electron-hole plasma in electrically pumped multiple-section GaN-based laser diodes, as demonstrated in previous FET-OPEN project FEMTOBLUE, to optically pumped magneto-excitons in InGaAs/GaAs quantum wells (QWs). On the other side, the original treatment by Dicke of the superradiance (SR) in an ensemble of two-level atoms shows an atomic superposition state. Recent communications, evoke the possibility of reaching highly entangled state during superradiant emission.