# What is a Quantum Internet? | QuTech Academy

What is a quantum internet? A quantum internet provides radically new

internet technologies that allows us to solve tasks which are impossible to accomplish

on the classical internet. As with any radically new technology, we cannot

yet foresee all applications of a quantum internet, but it already has quite a number of exciting ones. For example, it allows us to do absolutely

secure communication, secure identification, position verification, secure dedicated computing

and many others we will visit in other videos. So what does a quantum internet look like? On a quantum internet we don’t send classical

bits, 0’s and 1’s, but we will transmit qubits. But otherwise the basic elements of a quantum

internet do not look so different from a classical one. The first element of a quantum internet is

what we call an end node. An end node is basically your computer or

laptop or phone that is attached to the internet and that you use in order to run applications. So you need the end node

in order to use the quantum internet. As the name suggests, on a quantum internet we will

not use normal laptops, cell phones or computers, but instead we will use quantum computers. These quantum computers actually

don’t need to be very complicated. It turns out that most applications of a quantum internet

only require these end node quantum computers to be very simple and have less than 10 qubits. In fact for most applications they only need

to have one qubit. The reason why we typically do not need many

qubits is because a quantum internet draws its power from quantum entanglement. And already one qubit at each end point is

sufficient to have entanglement. In contrast on a quantum computer we always

need more qubits than can be simulated on a classical computer in order to do

something new and interesting. The next element of a quantum internet

is that, similar to a classical internet, we have all kinds of elements that allow us to

maximize the use of existing infrastructure. On a classical internet, not every computer

on the internet has a direct fiber connection to every other computer on the internet. But instead, fibers run through central points where there are switches that direct the bits

in the right direction. If you want to build a quantum internet,

then similar to a classical internet, you for example want switches

that are capable of switching single qubits. Now ideally we would like to send qubits

over very long distances; from any point on earth to any other point on earth. In order to achieve this we will need something

that is capable of sending qubits over long distances. This requires a very special form of repeater

called a “quantum repeater”. A quantum repeater works very differently

than the classical repeater. In a separate video you will learn all about

quantum repeaters. When realizing a quantum internet,

then just like on the classical internet, we will also need some control traffic. Basically next to the quantum communication

we will also use classical communication, for example to direct the qubits in the right

destination in the network. This is what a quantum internet looks like. Now, I have already mentioned that a quantum

internet allows us to solve tasks that are impossible to accomplish on a classical internet. Now the question is: what makes a quantum

internet, or what makes the transmission of qubits so much more powerful than what we have today? Qubits have very special features. For example, they cannot be copied,

making them ideal for security applications. Two qubits can also be in a very special state:

namely an entangled state. An entangled state between two qubits is the

essence of the power of a quantum internet. In order to understand entanglement

or why entanglement is so useful, it is sufficient to understand two very

fundamental properties of entanglement. So let me explain these two properties of entanglement

and why they give power to a quantum internet. The first feature of entanglement is that

it allows maximum coordination. So what does this mean? Two qubits can be entangled

even at very long distances. For example I can have a qubit in Delft,

which is entangled with a qubit very far away, for example in China. Now if I make a measurement on my qubit here in Delft and a friend of mine would make

the same measurement in China, then it will turn out that we will always get

the same outcome. You can think of a measurement

as asking a question to a qubit. For example, I might ask the qubit:

“Are you pointing left or are you pointing right?” Maximum coordination means that if I see the

outcome left in Delft, then immediately/instantaneously, if my friend in China makes the same measurement

the qubit will also be pointing to the left. And if I see it pointing to the right then

also in China it will be pointing to the right, even if the this answer is not determined ahead of time. In fact randomly we will get left-left or right-right, but the point is that the outcomes

will always be the same. And the amazing thing about entanglement

is that this is true for any measurement or any question we might ask. If I were to ask the qubit: “Qubit, are you red or blue?” Then we would have always observe

maximum coordination: red-red or blue-blue but never anything else. So the first feature of entanglement

is maximum coordination and it is this feature that makes

entanglement so suitable for tasks that require synchronization or coordination. The second feature of entanglement

is that it is inherently private. Because of course, you might be wondering

given that qubits are so powerful allowing this instantaneous maximum coordination, wouldn’t it be great if many qubits could be entangled. Now it turns out that only 2 qubits can be

maximally entangled with each other. So entanglement is inherently private. If I have a qubit here in Delft and the qubit

that it’s entangled with is somewhere in China, then you can think of this entanglement as a private

connection that nothing else can have part of. It is not possible for any other qubit anywhere,

to have any share of this entanglement between the Delft qubit and the qubit in China. It is this feature that makes quantum communication so fundamentally suitable for tasks

that require privacy and security. So entanglement gives power to a quantum internet, and in a later video we will see

how to use this entanglement to also send qubits using quantum teleportation.

If only humanity was smart enough to ask it something that didn’t involve greed.

So smart we are, that we have faithless people, supposedly creating things that they can’t understand.

We can’t even figure out a question to solidify its consciousness. That should be our first clue.

Great job. Good info, and well illustrated. Much appreciated. ✌️

I love you Stephanie 😘

One interesting point is that the presenter doesn't specifically state that the measurement of the qubit quantum state, say in Delft, is transmitted over the classical internet to the qubit quantum state measured in China, and vice versa.

Is the presenter implying that QE qubits can enable FTL (Faster Than Light) communications? Can we eventually communicate instantly with robotic exploration space probes either on the surface of Mars, or in orbit around it?