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.

3 thoughts on “What is a Quantum Internet? | QuTech Academy

  1. 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. ✌️

  2. 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?

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