Researchers over at Griffith University, University of Bristol, Cambridge and their counterparts at the Xi’an Jiaotong University in China have managed to find answers to the quantum key distribution (QKD), which could allow handhelds to communicate using the uncrackable quantum cryptography.

Before diving into the work carried out by the researchers here is a little primer for the uninitiated of what quantum cryptography is all about. Imagine A and B wanting to communicate without C listening in. If we take into consideration traditional cryptography, public key and private key based communications is the most secure, but it involves very big prime numbers which are basically huge math problems which would require a lot of computing power as well as time to solve. Computing has advanced to great extents to reduce the time required to solve these problems, which poses a ‘when will it be cracked’ question rather than ‘if it will be cracked’.

This is where quantum cryptography comes into play. Instead of finding ways to prevent decryption QKD stops the interception as it uses photos for transmission of keys. Laws of physics, specifically Heisenberg’s Uncertainty Principle guarantees that an eavesdropper wouldn’t be able to intercept the photons without changing or destroying them. Further up until now quantum communications were only possible through the use of top-notch quantum optics hardware found only in labs. Read on!

A paper published at Arxiv outlines the work carried out by the researchers and gist of the work is that they have managed to turn the whole QKD problem in a client-server architecture, splitting the overall work by assigning the heavy-lifting part to the server-side whereas the handheld client – be it smartphone, tablet or any other such device – is only required to carry out the last bits of the work.

The catch here is that none of today’s handheld devices would be able to support QKD as they would require special hardware – an on-chip polarization rotator, but this is not something that can’t be achieved. Further, as the devices can’t use QKD over the air, fiber tethering would also be required to send and receive the quanta.

To eliminate the requirement of quantum optics equipment at both the sender and receiver, the researchers have proposed that most of the quantum tasks be done at one end only. Giving an example, the paper notes that the sender would create the photons and sends them across to the receiver, who in turn would only need the capability to change the polarization of photons and send them back.

The QKD is based on a protocol dubbed rfiQKD, “reference frame independent quantum key distribution”, which effectively works without the need of aligning Alice and Bob’s equipment. “Instead Alice and Bob make measurements in random directions and then publish the list of directions for anyone to see. Only those measurements that happened to be aligned contribute to the code”, reads the paper.

[Source: MIT Technology Review]