We've spent a lot of time talking about quantum stuff lately. Some is just cool for its own sake, some of it could genuinely revolutionise the way we do things, but either way, quantum mechanics has already shown it can be applied to a range of practical uses. Add one more to the list - a US defence firm has come up with the idea of using photons to create highly-dense and principally unbreakable communications.
Traditional inter-sub communication usually makes use of low frequency radio signals in order to exchange security keys and send information. These frequencies can penetrate the sheer mass of the surrounding water, but severely limit the amount of data that can be exchanged to a mere handful of characters a second.
The solution, then, is to find a way to transmit more data underwater without compromising security. And so US defence group ITT went with photons.
The trick with photons, if you've been following along at home, is that they can be adjusted to have different quantum properties, while physically being more or less the same. In this case, photons could potentially be adjusted into '0' and '1' states at the quantum level. The added plus is that, by their nature, trying to intercept and observe the state of the photons post-broadcast would destroy their binary properties, meaning the photons would be useless for any sneaky people trying to listen in on secure communications.
Using the photons in, say, a laser would mean that large amounts of data (about 170mb a second) could be transmitted securely, allowing for video communications, and maybe the odd game of Call of Duty as well (ok, maybe not that last one).
In any case, the idea still seems to be just that, aside from a few simulations.
The real question, though, according to some experts, is whether photons will be able to be transmitted through water at any acceptable distance without degrading the signal.
Professor Josef Pieprzyk, the Director of the Centre for Advanced Computing - Algorithms and Cryptography (ACAC) at Macquarie University told PopSci.com.au that, while quantum key distribution itself was nothing new, punching a signal through water was.
"That could be a challenge. In this case they would need to use, probably, a powerful laser, but even if they used powerful enough lasers, you would still have a lot of noise at even 100m of water."
"In the ideal model, you should actually transport the single particle, we call it a qubit, in a complete vacuum from one side to another, because if something observes, it collapses and it does not go through. You know, this is physics. You cannot duplicate the same particle. So, this is actually a sort of security."
But then, he says, to make a workable system, you need to use a group of particles to ensure delivery, which also makes it more likely that photons will be intercepted.
The record for furthest quantum photon signal is 144 kilometres, through air. We'll have to wait for ITT to run experiments at Washington DC's Naval Research Lab to see if anything near that can happen in water.
