Physics team suggests possible way to make quantum cryptography available in handheld machines

(Phys.org) —A team of physicists at Bristol University in the U.K. has proposed a possible way to allow for quantum cryptography between a large station and a small hand held device. They describe such a technique in a paper they have uploaded to the preprint server arXiv.

Being able to encrypt data and the key that allows for unlocking it has become important in modern life. Companies spend millions attempting to protect sensitive information while hackers work non-stop trying to overcome such hurdles to access that information. The current system (RSA) is believed to be, at least for now, just ahead of the hackers. It relies on public key encryption of plain text and privately encrypted keys. This system has two weak points. The first is that it assumes that a hacker has not been able to gain access to a private key through nonconventional means and the second is that it's based on mathematical algorithms that can be cracked given fast enough computers. To gain the upper hand, cryptologists have turned to quantum key distribution (QKD), where quantum bits are used to represent private keys. The main advantage here is that according to the laws of physics, it should be impossible for a hacker to use the key without their interception being detected, which would prevent the sensitive data from being sent.

Up till now, the main hindrance to using QKD has been that it requires a lot of heavy duty equipment and a straight line mode of transport between the sender and receiver due to its sensitivity to noise. In their paper, the team from Bristol claim to have come up with a scheme that should allow a way to overcome such restrictions, at least on the receiver side. It's based on what they call a reference frame independent QKD protocol for polarization of qubits in polarization maintaining fiber—which in essence means they use math (based on measurements made in random directions) to describe a way for moving photons through fiber cables without disturbing their polarization

The team has not yet built such a device of course, that will need to be done by applied physicists, engineers and computer professionals—thus it's not yet a certainty that such a device will work as imagined. One sticking point in particular might be whether the real-world system is actually able to overcome the inherent noise sensitivity.

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