Good article on Ars as well:
Today, Richard Hughes and pals at Los Alamos National Labs in New Mexico reveal an alternative quantum internet, which they say theyve been running for two and half years. Their approach is to create a quantum network based around a hub and spoke-type network. All messages get routed from any point in the network to another via this central hub.
This is not the first time this kind of approach has been tried. The idea is that messages to the hub rely on the usual level of quantum security. However, once at the hub, they are converted to conventional classical bits and then reconverted into quantum bits to be sent on the second leg of their journey.
So as long as the hub is secure, then the network should also be secure.
The problem with this approach is scalability. As the number of links to the hub increases, it becomes increasingly difficult to handle all the possible connections that can be made between one point in the network and another.
Hughes and co say theyve solved this with their unique approach which equips each node in the network with quantum transmittersi.e., lasersbut not with photon detectors which are expensive and bulky. Only the hub is capable of receiving a quantum message (although all nodes can send and receiving conventional messages in the normal way).
That may sound limiting but it still allows each node to send a one-time pad to the hub which it then uses to communicate securely over a classical link. The hub can then route this message to another node using another one time pad that it has set up with this second node. So the entire network is secure, provided that the central hub is also secure.
The big advantage of this system is that it makes the technology required at each node extremely simpleessentially little more than a laser. In fact, Los Alamos has already designed and built plug-and-play type modules that are about the size of a box of matches. Our next-generation [module] will be an order of magnitude smaller in each linear dimension, they say.
Their ultimate goal is to have one of these modules built in to almost any device connected to a fibre optic network, such as set top TV boxes, home computers and so on, to allow perfectly secure messaging.