Multi-Party Quantum Communication May be Coming
Many people are looking forward to the day that quantum communication can be used to securely share information with another party. While that may sound great, there is a limitation to many of the current approaches, as only two parties can communicate with each other securely. Researchers at the University of Waterloo however have successfully entangled three particles, and this research could one day allow additional parties to be networked together.
Quantum entanglement involves having the properties of multiple particles so strongly coupled that measuring one can inform you about the state of the others. This is true no matter how separated the particles are. Typically only two particles are entangled, but by putting three photons in a Greenberger-Horne-Zeilinger (GHZ) state, all three particles were coupled and entangled. At this point the researchers placed one photon in a long optical fiber while the other two were sent to two trailers, 700 m away. This is far enough that the researchers were able to rule out that any information was being shared between the particles, when taking their measurements.
Previous work with quantum communication always focused on connecting pairs of particles, but with this we can start thinking in terms of multiple particles and a network of parties. Multipartite protocols will have to be developed to take advantage of such networks, but it will be interesting to see what is ultimately made possible.
Source: University of Waterloo