Here comes the world’s first ever multi-node quantum network

• Researchers in the Netherlands construct the world's first multi-node quantum network
• Thanks to Bob, Alice and Charlie, the quantum Internet takes a small yet huge step closer to reality
• Three connected quantum processors point the way to an exponential increase in computing power
• Next steps: quantum hardware, software and network protocols

Dutch scientists working at the quantum research institute QuTech in the city of Delft, southeast of The Hague in the Netherlands, have built the first ever multi-node quantum network by managing to connect three quantum processors. The nodes can both store and process qubits (quantum bits) and the researchers have provided a proof of concept that quantum networks are not only achievable but capable of being scaled-up in size eventually to provide humanity with a quantum Internet.

When that happens the world will become a very different place. With massive new and computing capabilities being made available via the power of sub-atomic particles, intractable problems that would currently take many years to solve (it they could be solved at all) using conventional silicon-based super-computers will be determined within seconds.

The ultimate goal is to enable the construction of a world-wide quantum Internet wherein quantum mechanics will permit quantum devices to communicate and conjoin to create large quantum clusters of exponentially great power easily capable of solving currently unsolvable problems at enormous speed. 

Qubits, the basic building blocks of quantum computers exist in a quantum state where, unlike traditional binary computing where a bit represents the value of either zero or one, qubits can exist both as zeros and ones simultaneously. Thus quantum computers can perform an incredible number of calculations at once but, due to the inherent instability of the quantum state they can collapse and disappear the instant they are exposed to an outside environment and must "decide" to take the value of a zero or one. This makes for the strong possibility that qubit calculations may, or may not, be reliable and verifiable and so a great deal of research is underway on error correction systems that would guarantee the results arrived at in a quantum calculations are true.

Say hello to Bob, Alice and Charlie, just don't look at them

A quantum Internet will come into being and continue to exist because of quantum entanglement, a remarkable physical property whereby a group of particles interact or share spatial proximity such that the quantum state of each particle cannot be determined independently of the state of the others, even when the particles are physically separated by great distances.

In other words, quantum particles can be coupled into a single fundamental connection regardless of how far apart they might be. The entanglement means that a change applied to one of the particles will instantly be echoed in the other. In quantum Internet communications, entangled particles can instantly transmit information from a qubit to its entangled other even though that other is in a quantum device on the other side of the world, or the other side of the universe come to that.

For this desired state of affairs to maintain itself, entanglement must be achieved and and maintained for as long as is required. There have already been many laboratory demonstrations, commonly using fibre optics, of a physical link between two quantum devices, but two nodes do not a network make. Thats's why QuTech's achievement is so important. In a system configuration reminiscent of the role routers play in a traditional network environment, the Dutch scientists placed a third node, which has a physical connection between the two others enabling entanglement between it and them. Thus a network was born. The researchers christened the three nodes as Bob, Alice and Charlie

So, Bob has two qubits: a memory qubit to permit the storage of an established quantum link, (in this case with Alice) and a communications qubit (to permit a link with node Charlie). Once the links with Alice and Charlie are established, Bob locally connects its own to qubits with the result that an entangled three node network exists and Alice and Charlie are linked at the quantum level despite there being no physical link between them. QuTech has also invented the world's first quantum network protocol which flags up a message to the research scientists when entanglement is successfully completed.

The next step will be to add more qubits to Bob, Alice and Charlie and develop hardware, software and a full set of protocols that will form the foundation blocks of a quantum Internet. That will be laboratory work but later on the network will be tested over real-world, operational telco fibre. Research will also be conducted into creating compatibility with data structures already in use today.

Another problem to be solved is how to enable the creation of a large-scale quantum network by increasing the distance that entanglement can be maintained. Until very recently that limit was 100 kilometres but researchers in Chinese universities have just ramped it up to 1,200 kilometres. 

The greater the distance of travel, the more quantum devices and intermediary nodes can be deployed and the more powerful and resilient a quantum network and Internet will become. That will enable new applications such as quantum cryptography, completely secure, utterly private and unhackable comms and cloud computing, the discovery of new drugs and other applications in fields such as finance, education, astrophysics, aeronautics, telecoms, medicine, chemistry and many others that haven't even been thought of yet.

It might even provide answers to the riddle of the universal oneness of which we are all a miniscule part. Maybe the answer to the question of life, the universe and everything will be 43, as calculated by the supercomputer Deep Thought rather than the 42 postulated by Douglas Adams in "The Hitchhikers Guide to the Galaxy". Even if that is the case, given localised quantum relativity effects and Heisenberg’s Uncertainty Principle it could easily be another number, until you look at it, when it turns into a living/dead cat.