Quantum Networks: What are they, how they can be used
The recent outbreak of WannaCry ransom malware brought up a lot of issues. The crucial one is that of the industrial and government networks vulnerability. Cyber security experts and authorities have long been seeking the dedicated as well as hack-proof network. The Israeli Ministry of Defense sponsored the first ever quantum network to be designed and built by Jerusalem university.
Wait, wait, what is quantum? And what advantages will it get over the old-school fiber-optic or wireless networks?
Quantum is the tiniest and undividable particle of matter, in our case – a particle of light called photon. A quantum possesses many amazing features that seem illogical from the first glance. For instance, it changes its qualities when looked upon. If our chairs were quantum they’d turn into kangaroos dozen times a day. In terms of data transfer, intercepting a quantum-ciphered piece of data changes it. And the receiver will understand the data was intercepted. But the hacker won’t be able to use the intercepted cipher key or password too because it is changed. A bit like stealing the fairy gold that turns shards and coals in daylight.
To send data in quantum scientists use the special laser that emits short impulses. The sender is called Alice and the receiver is called Bob. Physicists love romance, too. But there’s also Eve who is jealous of Bob and Alice and wants to ruin their relationship. For instance, Alice writes to Bob, “Let’s have dinner in our favorite place. The seafood restaurant.” Eve intercepts the message and reads it. But she doesn’t know that changing the route and reading the message ruins it. All she can get is a mess of letters like “fjowsdfyl;ksdf’an”.
Bob will be puzzled to get such a cryptic message from his girlfriend but he can call her back and ask for details. Eve will know nothing about the plans.
“I can’t quite grasp the idea”, I hear you saying, “Isn’t Bob an observer as well? If reading the message ruins it how can he get any at all? It’s rubbish!” And now we approach another amazing quality of photons – entanglement. Alice and Bob are entangled with each other and that’s why they can read the messages they send to each other. Because in the quantum world there’s no sending or getting. The moment one entangled quantum changes, the other copies it. Data in the quantum world is ubiquitous.
How so? Ok, I think, you all have once read a story about twins separated at birth and brought up without knowing of each other. And how they broke the same arm as kids or how they grew up and married on the same day to namesakes and how they get the same number of kids and gave them the same names and so on and so on. Quantums are these twins. Knowing what happened to one of them, we know for sure what the other experienced. Changing one of them we change the other the same way.
What’s more amazing is that the entangled quantums must not contact physically to experience the changes. This phenomenon is called quantum teleportation. It teleports not physical objects (no Star Trek gadgets here) but data, features and qualities. Lets’ take a pair of socks. The moment you put one sock on your right feet the other becomes left sock. You didn’t touch it, you didn’t take it from the box, all you did is put on one sock of the pair. And in doing this you changed the other one.
How the particles get entangled? The twins were born from the same parents, the socks came in a box and were picked up for today’s tennis match. The particles should collide to get entangled.
This is the victory! Hackers of the world are defeated forever! Or are they? Not quite, we’re sorry to say. For example, the quantum message cannot be forwarded. Forwarding means changing the route and this ruins the message altogether. Alice, too, cannot write to anyone but Bob. Poor Alice!
The Los Alamos lab scientists has suggested the model of network that features the central hub. Every message goes first to this hub and then to other destinations. Alice can write to Charlie, Dolly and Frank. But here is where the other issue emerges.
Namely, the photons nature. As they travel along the fiber-optic cable they are vanishing, they’re dissolving into the environment. The maximum distance for quantum internet is within 150 km. So Bob really, really has to live next door to Alice. The record distance in the experiment of 2015 conducted by American and Japanese universities is 144 km. No photon lives beyond this limit.
The short life of the particles determines the data properties. Photons can transfer codes, keys but no big data like this article or a picture to say nothing of the 4k video. Alice can’t share her Instagram with Bob and show her cat.
Nowadays there are two ways to overcome the barrier. One is to install amplifiers every 100 km and the other is to cool down the cables and to use the rare materials like molybdenum for them. Suffice it to say that making the cables from gold and diamonds would have come cheaper. So the quantum internet can be used within the lab, the military headquarters or banking network provided that it covers a compact area.
Right now transferring codes, keys and sensitive banking data is the only way quantum networks are used. There are companies like Id Quantique, MagiQ, Smart Quantum which provide the industry class solutions.
Still, there’s a long way to go till our hospitals can afford the quantum network and storage. Talking of which, read about quantum computers next! Stay tuned!