Quantum Networks: What are they, how they can be used

Quantum Networks: What are they, how they can be used

The recent outbreak of WannaCry ransom malware created a lot of issues. The most crucial being that of the industrial and government network’s vulnerability. Cyber security experts and authorities have long been seeking a hack-proof network. The Israeli Ministry of Defense sponsored the first ever quantum network to be designed and built by a university in Jerusalem.

So, what is a quantum, and what advantages will it hold over fiber-optic and wireless networks?

A quantum is the smallest particle of matter, which is undividable. In our case, a particle of light called a 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 like a quantum, they’d turn into kangaroos a 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 that was intercepted. However, the hacker won’t be able to use the intercepted cipher key or password because it is changed. This is a bit like stealing the fairy gold that turns into shards and coals in daylight.

To send data in quanta, scientists use a special laser that emits short impulses. Let’s say we have a sender named Alice and a receiver named Bob. Physicists love romance, too, afterall. 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. However, 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”.

Image: habrastorage.org/files/718/794/d40/718794d4069f42a3af747854b118f82b.jpg

Bob would 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 receiving. The moment one entangled quantum changes, the other copies it. Data in the quantum world is ubiquitous.

How so? You have all probably read a story about twins separated at birth that grew up without knowing of each other. How they broke the same arm as kids, grew up and got married on the same day to namesakes, and how they have the same number of kids and gave them the same names. Quanta are these twins. Knowing what happened to one of them, we know for sure what the other experienced. By changing one of them, we change the other in the same way.

What’s more amazing is that the entangled quanta do not need to physically contact each other 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. Let’s take a pair of socks. The moment you put one sock on your right foot, the other becomes a left sock. You didn’t touch it, you didn’t take it from the box, all you did is put on one sock from the pair. In doing this, you changed the other one.

How did 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, a 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 have suggested the network model 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.

The issue, namely, is 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 150 km. So, Bob 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 and keys, but not a large amount of data like this article or a picture, to say nothing of 4k video. Alice can’t share her Instagram with Bob, for instance.

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 by using rare materials like molybdenum. Suffice it to say that making the cables from gold and diamonds would be cheaper. So, quantum internet can be used within a lab, military headquarters, or for a 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, and Smart Quantum which provide the industry class solutions.

Still, there’s a long way to go before our hospitals can afford the quantum network and storage. Speaking of which, read about quantum computers next! Stay tuned!