Remote quantum dots now swap entanglement using only photons

Researchers from seven countries, including Italy, Austria and Brazil, have demonstrated entanglement swapping between two remote quantum dots located in separate laboratories. The experiment relied entirely on the exchange of polarization-entangled photons to connect the dots, a key step toward building scalable quantum networks without the need for direct interaction. This all-photonic approach enables the swapping of entanglement, projecting the state of remote photons into a maximally entangled state, and accounts for differing photon energies across network locations. The work establishes a foundation for quantum repeater networks and protocols reliant on quantum memories. The implementation of entanglement swapping between quantum dots positioned in separate laboratories relied on a radiative cascade process, specifically the biexciton-exciton transition within the semiconductor material. This cascade generates highly entangled photon pairs deterministically, exhibiting high indistinguishability and a record-low probability of emitting multiple photons, qualities essential for reliable quantum communication. Researchers harnessed this phenomenon to perform a Bell state measurement, a critical operation for transferring quantum information between the remotely located dots. The experimental setup involved directing photons emitted from each…