What is meant by teleportation

ETH researchers are not yet able to “beam” objects or people made of flesh and blood through space, as shown in science fiction films. However, they managed to teleport information from A to B - for the first time on a chip, similar to a computer chip.

Physicists at ETH Zurich have succeeded for the first time in teleporting information in a so-called solid-state system. The researchers succeeded in doing this on a chip that is similar to a conventional computer chip, with the essential exception, however, that the information on it is not stored and processed according to the laws of classical physics, but rather according to those of quantum physics. In a study published in the latest issue of the journal Nature, the researchers succeeded in teleporting information over six millimeters from one corner of the chip to the opposite corner. This nota bene without physical particles having to travel from the sender corner to the receiver corner during the transfer of information.

“In ordinary telecommunications, information is transmitted via electromagnetic impulses. For example, pulsed radio waves are transported in mobile communications and pulsed light waves in fiber optic connections, ”explains Andreas Wallraff, professor at the Laboratory for Solid State Physics and head of the study. With quantum teleportation, on the other hand, one does not transport the information carrier itself, but only the information. This is done by using quantum mechanical properties of the system, in particular the entanglement of the transmitter and receiver unit. This means a connection that seems “magical” to non-physicists and that exploits the laws of quantum physics.

"Like beaming"

To prepare for quantum teleportation, the sender and receiver units are brought into an entangled state. The two units can then be physically separated from one another - the interlocked state is retained. During the actual experiment, the physicists program quantum mechanical information in the transmitter unit. Because the two units are interlinked, this information can also be read in the receiver unit. "Quantum teleportation is comparable to beaming in the science fiction series Star Trek," says Wallraff. "The information does not travel from point A to point B. Rather, it appears at point B and disappears at point A when you read it at point B."

In the ETH physicists' experiment, more information was transported to the recipient than would have been possible in the traditional way. This enabled the researchers to prove that the information about quantum physical effects was transmitted through teleportation.

In the experiment, the transmitter and receiver units were small superconducting circuits on a seven by seven millimeter chip. The scientists brought the units into an entangled state using controlled pulses with microwave photons. In order for the quantum physical properties to take effect in the system, the scientists had to cool the chip with helium to temperatures very close to absolute zero during the experiment.

High transfer rate

The distance of six millimeters over which the ETH researchers teleported may appear short in comparison with other teleportation experiments. A year ago, for example, Austrian scientists succeeded in teleporting information over more than a hundred kilometers between the two Canary Islands La Palma and Tenerife. However, this and similar attempts were fundamentally different, since they were optical systems with visible light. The ETH researchers, on the other hand, have succeeded for the first time in teleporting information in a system with electronic circuits. "That is interesting because such circuits are important elements for the construction of future quantum computers," says Wallraff.

Another advantage of the system developed by the ETH scientists: It is extremely fast and significantly faster than most previous teleportation systems. This means that around 10,000 quantum bits can be transmitted per second. A quantum bit is the unit of information in quantum systems.

Always correct information transfer

In addition, the researchers succeeded in finding a solution for a horse's foot in quantum mechanical information transfer: namely, the sender and receiver units can be entangled in four different ways - in four so-called Bell states. Depending on the Bell status, the information is read out in different ways by the recipient. From a statistical point of view, the correct information is read out directly in only one of four cases.

The ETH researchers' system can deal with this problem. After the information has been teleported from the sending unit to the receiving unit, the two units exchange data about their state of entanglement. This means that the correct information can be read out in all four possible cases.

«Important future technology»

Next, the researchers want to use their system to increase the distance between the transmitter and receiver. First, they want to try to teleport information from one chip to another. And in the long term, the aim is to research whether it is possible to operate quantum communication with electronic circuits over greater distances, as is now being done with optical systems.

"Teleportation is an important future technology in the field of quantum information processing," says Wallraff. In this way, for example, information on a quantum chip or in a future quantum processor can be transported from one point to another. Compared to today's information and communication technologies, which are based on classical physics, quantum physical information has the advantage that the information density is much higher: More information can be stored in quantum bits and processed more efficiently than in the same number of classical bits.

Bibliography

Steffen L, Salathe Y, Oppliger M, Kurpiers P, Baur M, Lang C, Eichler C, Puebla-Hellmann G, Fedorov A, Wallraff A: Deterministic quantum teleportation with feed-forward in a solid state system. Nature, 2013, 500 : 319-322, doi: 10.1038 / nature12422