Teleportation works for the first time between remote qubits

computer science

Writing the Technological Innovation website – 05/30/2022

Since Qubits do not have any physical interconnections, they form the beginning of a quantum network that is inherently secure.
[Imagem: Qutech/EVA Explainer]

quantum internet

After proving that quantum teleportation can be practical, secure, and reliable and used to create the first quantum network with more than two nodes, researchers at Delft University of Technology in the Netherlands took the missing step in proving the quantum internet. can grow.

Sophie Hermans and her colleagues first used quantum teleportation to transfer information between distant qubits, making things even more like Star Trek’s mode of transportation. , it doesn’t matter.

In fact, the quantum teleportation protocol owes its name to the similarities with teleportation in science fiction films: the quantum bit disappears on the sender’s side and appears on the receiver’s side.

Because information does not have to travel through space, there is no chance of being lost or captured, making it a crucial technique to ensure the true quantum encryption of future networks. it will be faster than current optical networks, but will be inherently secure.

Several groups have already demonstrated this teleportation using various types of qubits. However, in all cases, the qubits were either sideways or interconnected in some way.

Now, the phenomenon worked between distant qubits, with no direct connection between them.

That internet

Information is teleported between remote qubits without a direct connection.
[Imagem: Scixel for QuTech]

quantum teleportation

To be able to teleport information between quantum bits, some components are needed: a quantum entanglement link between sender and receiver, a reliable method of reading qubits, and the ability to store qubit values ​​temporarily.

To be able to do it for the first time among non-adjacent qubits — that is, on a network — the team used three separate qubits built inside diamonds that are able to store data for a longer period of time.

The teleportation has three steps (the three qubits were named Alice, Bob and Charlie). First of all, the “teleporter” needs to be prepared, which is to create an intricate situation between Alice and Charlie – Alice and Charlie have no direct physical connection, but both are directly connected to Bob.

Once entangled with Alice, Bob saves his data and then creates an entangled situation with Charlie. What “magic” works: By making a special measurement on his processor, Bob somehow “sends” his state. Results: Alice and Charlie are connected and ready to use the teleporter!

The second step is to create the message to be teleported – a quantum bit – and this is done in Charlie. This could be, for example, ‘1’ or ‘0’ or to show that other intermediate quantum values ​​- teleportation works in a generic way, the researchers repeated the whole experiment for different quantum bit values.

The last step is the actual teleportation from Charlie to Alice. To do this, Charlie makes a unified measurement with the message in his quantum processor and half of his complicated state (Alice has the other half). What happens then is something that is only possible in the quantum world: As a result of this measurement, the information disappears from Charlie’s side and immediately appears from Alice’s side.

That internet

The diamond qubits are inside the black cylinder, cooled to -270 ° C to reduce environmental noise.
[Imagem: Marieke de Lorijn/QuTech]

Teleported data is encrypted

It seems a bit complicated, but the thing is not over yet: the fact that the quantum bit was encrypted in the transfer, the key to that encryption was determined by the result of Charlie’s measurement.

Charlie then sends the measurement result to Alice, and then Alice performs the corresponding quantum operation to decipher the quantum bit. For example, with a “bit flip”: 0 becomes 1 and 1 0.

Once Alice has performed the correct operation, the quantum information is suitable for later use. Teleportation was a success!

The group now wants to focus on reversing the first and second steps of the teleportation protocol, which is to create (or receive) the quantum bit to be teleported first, and then to prepare the teleporter for teleportation.

Reversing the order is particularly difficult because the quantum information to be teleported must be stored while the entanglement is being created. However, this has a significant advantage: teleportation can be done entirely on “request” (“Two to climb, Scotty”).

This is important, for example, if quantum information is the result of a difficult calculation or if teleportation has to be done multiple times. In the long run, this type of teleportation will therefore serve as the focus of the quantum internet.

Bibliography:

Article: Qubit teleportation between non-side nodes in a quantum network
Authors: Sophie LN Hermans, M. Pompili, HKC Beukers, S. Baier, J. Borregaard, Ronald Hanson
Magazine: Nature
DOI: 10.1038 / s41586-022-04697-y

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