While this was in the news last week, only recently have I had a chance to sit down and read more about what the Swiss are up to. There’s a pretty good summary piece at Scientific American.com. Here’s a short summary from that article:

With quantum encryption, the sender encodes the encryption key on an individual quantum particle, such as a photon or electron, and sends that particle via a fiber-optic line to its destination. Information about key characteristics of the particle—such as its size or level of polarization—is sent to the destination as well. If the particle that arrives is distorted in any way, it is discarded and another key is sent. This protects quantum encryption and quantum key distribution from third-party eavesdropping because a particle cannot be intercepted without changing its quantum state.

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The quantum encryption work being done in Switzerland will be an important learning experience, particularly because the technology is still in its early stages of development, Habif says. Quantum key distribution systems available today work only over short distances and require an exponential amount of computing and network resources as that distance grows. “If you give the field five to 10 years, you will see the beginnings of a scalable quantum key distribution system,” he says, adding that a quantum signal cannot be amplified today because a repeater would destroy the photons and the data they carry as it inspects the photons. “You need a quantum repeater that will preserve the fidelity of the quantum information as it moves through the network.” Of course, the presence of such a repeater could also weaken the sanctity of the encrypted transmission if the fiber-optic network is not properly secured.

Here’s a copy of the press release that announced this development.