How does the United States compete with China for this and what is the advantage of quantum cryptography? We talked about a future topic with Antonín Černoch of the ASCR Institute of Physics (Here(In the current issue of A / Science and Research)Here), Published by the Academy of Sciences of the Czech Republic.
The spaceship Enterprise crew blasted from orbit to the surface of an unknown planet. A conveyor is used to transport it to the specified location. After completing the mission, he found himself again in a tanker on board the ship. First, light cones appear, from which the bodies of space heroes form after a while. We have come across a similar type of travel not only in the Star Trek series. Just remember Rumburak or Hell moving in the fairy tale there are no jokes with demons.
Teleportation in the form of an intangible transfer of something at a distance remains the domain of science fiction, fantasy or fairy tales. As such, however, it is not merely a fiction of writers or filmmakers. On the contrary – it is receiving a great deal of scientific interest. Last year, at the UP’s School of Science joint laboratory Olomouc Optics and the ASCR Institute of Physics, researchers ran an experiment in which they were the first in the world to experimentally validate the controlled simultaneous transfer of quantum bits. .
Naturally, when we read these words, the aforementioned scene from Star Trek comes to mind. The reality is a lot more realistic, but it’s still pretty cool. Scientists did not transfer a specific particle, but rather its quantum state, which we can imagine as information. The researchers encoded it into a photon, because they usually work with this particle in the Olomouc Optical Laboratory. They used three quantitatively entangled photons.
Connecting Alice and Bob
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The characters of Alice and Bob were invented by cryptists in the 1970s, which over time began to be used as an illustration of the communication between points A and B. Imagine that Alice wanted to teleport Bob the characteristics of the photon marked with the letter P. Requires a double pair of two photons A and B. Photon A by Alice, and Bob takes photon B. The teleportation consists of Alice making a combined measurement on photons A and P. Thus, the properties of photon P are automatically reflected in photon B, which Bob possesses thanks to the quantum coupling. But this is not enough. To complete the teleport, Alice must let Bob know exactly what he measured in the classic way. Need to call or email him. With the aforementioned measurement, the two photons P and A automatically disappear and only photon B remains, which – after a slight modification depending on the result of Alice’s measurement – is identical to the original P photon.
Or another example – we take two dice in our hand and roll them together at the same time. We’re rolling for the first time, falling thirty, falling sixty again, fifty thirds, etc. The numbers on the dice drop randomly, but they always match. There is a relationship between the dice. The analogy of this symmetry between quantum particles is called quantum coupling. It’s the magic of quantum mechanics. One of the particles may be in New York, the other in London, but thanks to the common wave function, they behave as a whole. Photons connected in this way can be formed, for example, into a special non-linear crystal in which the laser beam is illuminated.
Scientists in Olomouc were the first to perform controlled teleportation of quantum bits with an accuracy of 83%. So far, quantum teleportation has occurred between two users. One of them sent information and the other received, and their exchange was not affected. So, experts from the Joint Optics Laboratory created a group of three users, each of whom always decided whether to transmit the quantum state or not – thus transferring the information between the remaining users. It plays the role of a kind of control unit in the system. Therefore, this type of teleportation is called censorship. It is important that the specific communication triangles can be joined together and create a complete 2D network, which could become the basis for the global quantum internet in the future.
The struggle for quantum primacy
The USA and China are the furthest in their development – competing for dominance in quantum informatics. The White House announced last year that it was funding a strategic vision for quantum networks in the United States. The plan assumes that private companies and national laboratories will collaborate in basic and applied research over the next five years. Quantum network prototypes already exist, and in suburban Chicago we’ve assembled an 83-kilometer loop.
China is not far behind. It identified quantum informatics as a key area in its thirteenth five-year plan, which jumped in last year. Meanwhile, a quantum network connected the cities of Beijing and Shanghai more than 1,200 kilometers away. In 2017, the Chinese were able to teleport photons between a station in Tibet at an altitude of more than 4,000 meters and a satellite in an orbit at an altitude of 1,400 kilometers. Chinese experts predict that “quantitative hegemony” may determine the future of international politics. “These foreign examples are two-way communication lines. We did a three-way job, while one could control the communication between the other two,” explains Antonin Ernoch of the ASCR Institute of Physics.
Quantum teleportation refers to the transport of quantum bits, the so-called qubits. It is a much more complex vector of information than a traditional bus, based on the principle of ones and zeros. The quantum bit can be one and zero. “The quantum state can hold an infinite number of classical bits,” explains Antonin Ernouch. If we allow qubits to communicate, an unimaginable amount of information interacts with each other. Therefore, the laws of quantum informatics are not easy to understand.
The quantum internet will be more secure. Whenever anyone breaks into a communications network, it will be activated immediately. As for quantum mechanics, it is true that any interaction in a network also alters it. For example, a hacker attack could affect any of the connected users, regardless of their remoteness. As a result, the destroyer will be located or the connection will simply be lost. After all, many promise possibilities unprecedented since quantum cryptography. The work of Olomouc scholars can contribute to practical use in this field as well.
Engineers are on the move
Antonin Ernoche and his colleague Karel Limmer were based on a theoretical suggestion of quantum state teleportation from Polish collaborator Artur Parasinski. “We made it viable. Building the same experiment did not take that long again, because it continued in our previous multi-photon experiments,” says Antonin Ernoch. The results of the work have been published in the international journal Physical Review Letters. This is basic research, its practical use requires the invention of engineers who come up with a communication protocol and skillfully combine everything.
Communication threads are needed to transmit quantum bits to the Internet. In standard optical networks, the signal is amplified at certain distances in what are called repeaters. However, quantitative information cannot be amplified without being destroyed. Therefore, quantum repeaters are used to extend the contact distance, which works on the principle of simultaneous transmission.
Will we ever see an effective transformation in space, as we know it from popular movies? Antonin Ernoch is skeptical. Only information can be conveyed, not tangible things. “It is not possible to physically transport an atom from one place to another.” So we’re likely only going to look at similar events on movie and television screens.
This article and other interesting texts can be found in the journal A / Science and Research published by the Academy of Sciences of the Czech Republic Here.
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