This week saw news that Chinese scientists had entangled eight photons, breaking the previous record of six.
This is not four entangled pairs, but eight photons that have been sequentially entagled using a non linear crystal.
The team, based at the University of Science and Technology of China at Hefei, has submitted an account of their work to arXiv.
In it, they describe how they created an initial entangled pair of photons by sending a single photon through a non-linear crystal. One of these photons was then sent back through the crystal, creating a second pair and total of three entangled photons. This was repeated until eight photons had been entangled.
Entangled pairs generally do not last long, and according to PhysOrg, the novelty in this research is based on the Chinese team’s ability to stabilise the entangled photons for long enough to repeat the entanglement process so many times.