Satellite quantum communication circles closer

July 30, 2010 | Source: New Scientist Tech

A new quantum protocol is the first that promises to work independently of the orientation of spin on pairs of entangled photons shared between a sender and receiver, which will prove vital if quantum communications are ever to be sent via satellites (a spinning satellite’s sense of up and down changes over time, making it harder to interpret a photon’s spin and establish a key).

A team at the University of Bristol in the UK has invented a protocol independent of orientation that exploits the fact that photons can have an entangled circular polarization as well as entangled spin. Circularly polarized light can be imagined to corkscrew either clockwise or anticlockwise along its axis of travel. The two forms are readily identified regardless of the receiver’s orientation.