# Wen Quantum Internet ? Well... What is Quantum Internet? How does it work? Mostly asked question: When? Quantum computers are still under development. But the Quantum Internet is closer than you think. The capacity to transport quantum information (quantum bits) across network nodes is what gives a future quantum Internet its power. This will enable a wide range of applications, including securely exchanging private information, connecting several quantum computers to improve processing capacity, and the use of extremely accurate, coupled quantum sensors. A quantum network's nodes are made up of tiny quantum processors. Sending quantum information between these machines is a difficult task. One option is to communicate quantum bits through light particles, however due to the unavoidable losses in glass fibre cables, especially over long distances, the light particles will almost certainly not arrive at their destination. Because simply copying quantum bits is inherently impossible (no cloning theorem), the loss of a light particle means that the quantum information is irreversibly gone. Teleportation offers a better way of sending quantum information. The protocol for quantum teleportation owes its name to similarities with teleportation in science-fiction films: the quantum bit disappears on the side of the sender and appears on the side of the receiver. As the quantum bit therefore does not need to travel across the intervening space, there is no chance that it will be lost. This makes quantum teleportation an crucial technique for a [future quantum Internet](https://www.youtube.com/watch?v=vBjxI-5Fb4U&t=3s). Puff... Too many weird words so far. “Let me tell you something really cool, Our Quantum World” # Our Quantum World We’ve invented forms of communication and constantly evolved how we interact with each other. To build a quantum network, we need repeaters like routers that we use to connect internet now. Actually we have been using classical repeaters over centuries such as smoke signals, african drums and optical signals under the sea.Most common princible underlying techniques sharing information over the distances is duplicate & amplifying classical signals. However, In our Quantum world things are slightly different. We have beautiful no clonning theorem which enables us to achieve perfect security. Physicallly unknown quantum states cannot be perfectly clonned by an eavesdropper so no one can copy information thanks quantum mechanical laws. This is also our biggest challenge while building robust quantum networks. We will come back to this later.. [To mention another realistic challenges](/https://www.youtube.com/watch?v=M3v9YPs2cAg). We also have loss errors and operation errors. * **Loss errors:** mostly fiber loss approx. 20km, coupling & detector inefficiency. * **Operation errors :** channel decoherence, memory errors, local gate/ measurement errors. As you can imagine, we have a quite work to do here. Let's look at the bright side of our Quantum World : [Quantum Entanglement](https://www.youtube.com/watch?v=aOiIgSd7G2o) Quantum Entanglement something we cannot see in classical world, it only occurs in quantum world. Practically entanglement means that the state of a second qubit (that can be ‘1’ or ‘up’) is dictated by the state of a first qubit (i.e. ‘0’ or ‘down’). Entangled particles such that properties like position, momentum, spin, and polarization can be shared between them. This entanglement can be used for generating secret keys for private communication, or teleportation of a quantum state between far away parties. This wonderful properties give us chance to build quantum networks long distances and get closer to achieve quantum internet. Here is main ingredients of Quantum Internet: * [Entanglement generation & distillation](https://www.youtube.com/watch?v=ZcfMJBtCwQY) * [Quantum Teleportation & entanglement swapping](https://www.youtube.com/watch?v=hxDYq09mWTo) * [Quantum error correction](https://www.youtube.com/watch?v=4hWUIGZh6WE) # # Step by step :Quantum Teleportation A quantum entangled link between the sender and receiver, a reliable way to read out quantum processors, and the capacity to temporarily store quantum bits are all necessary for the ability to teleport quantum bits.There are three steps to teleportation. ***1- Set up teleporter :*** First step, the "teleporter" must be setup, which requires Alice and Charlie to get entangled. Although Alice and Charlie have no physical relationship, they are both immediately connected to Bob. Alice and Bob do this by establishing an entangled state between their processors. Bob then records his portion of the entangled state. Bob then enters an entangled state with Charlie. Bob sends the entanglement on its way by performing a particular measurement on his CPU. As a result, Alice and Charlie have become entangled, and the teleporter is ready for operation! ![](https://i.imgur.com/pkkqReh.png) ***2- Create message:*** The second step is to generate the "message" — the quantum bit — that will be transported. This might be a '1' or a '0,' or any of a number of different intermediate quantum values. Charlie is in charge of preparing this quantum information. To demonstrate that the teleportation works in general, the researchers repeated the entire experiment with different quantum bit values. ![](https://i.imgur.com/ga1or7v.png) ***3- Actual teleportation :*** The third step is for Charlie to teleport to Alice. Charlie does a joint measurement with the message on his quantum processor and on his side of the entangled state for this reason (Alice has the other half). What occurs next is something only possible in the quantum world: as a result of this measurement, the information disappears on Charlie's side and reappears on Alice's side.(Real Magic..) --- ![](https://i.imgur.com/16ncNMh.png) Wait.. we are not done yet. The quantum bit was encrypted during transport, and the key is determined by Charlie's measurement result. As a consequence, Charlie sends the measurement result to Alice, who then performs the required quantum operation to decode the quantum bit. For example, a "bit flip" converts 0 to 1 and 1 to 0. The quantum information is now ready for use when Alice has completed the right procedure. The teleportation has accomplished! ![](https://i.imgur.com/M5dhFpO.png) *Alice, the receiver of the teleported quantum information. Inside the black aluminium cylinder, the diamond sample is cooled to -270°C, to reduce the noise from the environment and enable the quantum control. [QuTech, Experiment Setup]* # Where we at now ? [Delft University of Technology researchers](https://qutech.nl/lab/hanson-lab/research-highlights/quantum-teleportation-across-a-network/) have successfully teleported quantum information across a basic network. This is the first of its type, and it represents a critical step toward a future quantum internet. This accomplishment was made feasible by much increased quantum memory and the improved quality of the quantum connections linking the network's three nodes. Sounds great, isn't? Official paper published in [Nature ](/https://www.nature.com/articles/s41586-022-04697-y) on May 2022.[ Prof. Hanson's Lab](https://qutech.nl/lab/hanson-lab/) is known for cutting edge of quantum science, enabling exploration of open scientific questions as well as pushing the state of the art in quantum information processing. Quantum Internet is getting out of the labs day by day. Last record on July 06 2022, [Entangling single atom over 33 km](https://www.nature.com/articles/s41586-022-04764-4) achieved by an experimental setup at Ludwig-Maximilians-University Munich. Using current fiber optics without building new infrastructure make this achievement more important milestone and it is quite close to our in use telecom standard. Yes! answer is in your lifetime .. Keep wondering, What the future holds for us ? Many more than we can imagine. Stay curious and think quantum!