It has been demonstrated that quantum information can be teleported across a rudimentary network by researchers in Delft.

In the future, a quantum Internet will be possible through this first of its kind. Enhanced quantum links between the nodes of the network and improved quantum memory contributed to this breakthrough. Today, Delft University of Technology and the Netherlands Organisation for Applied Scientific Research (TNO) researchers published their findings in Nature as a result of their collaboration at QuTech.

A quantum Internet will be able to send quantum information (quantum bits) between its nodes of applications such as securely sharing confidential information, linking several quantum computers together to increase their computing capability, and the use of highly precise, linked quantum sensors.

Quantum networks are composed of small quantum processors called nodes.

Quantum information cannot be sent easily between these processors. Quantum bits could be sent by light particles, but glass fibre cables always lose light due to their inherent losses, especially over long distances. So the light particles are likely to not reach their destination. In the absence of a light particle, quantum information is irrecoverably lost, because it is fundamentally impossible to simply copy quantum bits.

Quantum information can be sent more effectively through teleportation. A quantum bit disappears on one side of the sender and reappears on the other in this protocol for quantum teleportation. The name is derived from similarity to teleportation in science-fiction films. Due to the lack of space between the quantum bit and its destination, there is no risk of it being lost. A quantum Internet will be dependent on quantum teleportation in the future.

There are three steps involved in the teleportation process. Creating an entangled state between Alice and Charlie is the first step in preparing the “teleporter”. Bob is directly connected to Alice and Charlie, even though they do not have a direct physical connection. It achieves this by entangled states between Alice and Bob’s processors. The entangled state is then stored by Bob. A state of entanglement is then created between Bob and Charlie. The entanglement is then sent on by Bob’s processor as a result of a quantum mechanical “sleight of hand.” The teleportation consists of three steps. First, the “teleporter” has to be prepared, which means that an entangled state must be created between Alice and Charlie. Alice and Charlie have no direct physical connection, but they are both directly connected to Bob. For this, Alice and Bob create an entangled state between their processors. Bob then stores his part of the entangled state. Next, Bob creates an entangled state with Charlie. A quantum mechanical “sleight of hand” is then performed: by carrying out a special measurement in his processor, Bob sends the entanglement on as it were. There now exists an entanglement between Alice and Charlie, and the teleporter is ready for use.

A second step is to create the “message” – the quantum bit – that is to be teleported.

Various intermediate quantum values can be used for this, like ‘1’ or ‘0’. The information is prepared by Charlie. Researchers repeated the entire experiment with multiple quantum bit values to provide evidence that teleportation works generically.

A teleportation takes place in step three between Charlie and Alice. A joint measurement is done by Charlie and Alice with the message on their quantum processors (Alice has the other half of the entangled state). A quantum event occurs when there is a measurement on one side and an instantaneous change on the other: the information disappears on Charlie’s side, yet appears immediately on Alice’s side.

If you think something is completed then, you could not be more mistaken. Charlie’s measurement result is the key to unlocking the quantum bit after it is transferred. Alice decrypts the quantum bit after Charlie sends the measurement result to her. A “bit flip” for example, converts 0 to 1 and 1 to 0. Alice is now ready to use the quantum information after she has implemented the correct operation. Teleportation has been accomplished. 

The quantum internet is a big step forward, but we’ll need a lot more nodes to build the networks we’ll need for everyday use. Nonetheless, a telephone was the first piece of equipment in the development of today’s global communications network. 

Reference:

Delft University of Technology. (2022, May 25). Researchers teleport quantum information across rudimentary quantum network. ScienceDaily. Retrieved June 23, 2022 from www.sciencedaily.com/releases/2022/05/220525131156.htm