Quantum cryptography could be the star feature of your next cellphone. The first pocket-sized quantum encryption device has been created in collaboration with the Finnish phone-maker Nokia, and could let you send completely secure messages – although you will need to plug it into a quantum phone booth to do so.

Secure internet transactions mostly use public key cryptography, which is pretty good but can in principle be hacked by a sneaky eavesdropper or someone with a powerful enough computer. Using a quantum key, which cannot be duplicated without destroying the original, could make codes unbreakable. However, so far only banks and other big corporations can afford the bulky, expensive equipment required.

Now, an international team led by Anthony Laing at the University of Bristol, UK, has shrunk the quantum encoder by splitting the traditional system in two. A large “server”, which could one day be about the size of a case of beer, would contain the bulky elements like a laser and a single-photon generator.

The server would send photons through a fibre-optic cable into a tiny device which could be embedded in a mobile phone. The device includes a waveguide that alters the state of photons passing through it, encrypting the message. It then spits the altered photons out into the fibre-optic cable and back to the server.


Just plug in

To send data with complete security, you would just plug in your phone. It’s like using an ATM, says team member Mirko Lobino at Griffiths University in Brisbane, Australia. It could be used to make secure financial transactions or transmit sensitive data like health records.

Ben Buchler at the Australian National University in Canberra says the idea makes quantum cryptography a more practical option. He says people should be looking for something completely secure, especially with the recent revelations that the US National Security Agency might have back-door access to traditional encryption techniques. The possibility of quantum computers on the horizon would make current encryption obsolete.

Lobino says Nokia are interested in integrated quantum technology and have already patented the system, although he doesn’t know if they will be using it in a commercial product.

Journal reference: Physical Review Letters, DOI: 10.1103/PhysRevLett.112.130501