The world of Quantum Mechanics , the part of physics that studies how light and matter behave on the smallest scales, could not be more puzzling. It is full of realities familiar to scientists but "impossible" for the rest of us mortals. One of these is what Einstein called the "spooky distance reaction," a phenomenon that allows photons to "talk" to each other instantly, no matter how far away they are.
This disturbing behavior led some to think that it was possible to transport people and objects at a distance, without having to move them, using the so-called teleportation. But the mechanism that allows the crew of the Enterprise, in "Star Trek", to vanish in the ship and materialize on the surface of a planet instantly, belongs today to the field of science fiction.
Neither theory nor any current experiment is capable of coming close to a technology that can convert matter, let alone a living being as complex as Mr. Spock, into a signal that can then be transformed into matter in another location.
However, information teleportation is not science fiction . It is a known reality since 1993, and today there are already companies that use it to create theoretically indecipherable communication networks. There are also scientists who study it to create quantum computers, computers that in a matter of years will multiply the capabilities of today's most powerful supercomputers. And not only that, on August 16 China made a great leap in this technology after launching the first quantum satellite into space. From up there, they will test the phenomenon of teleportation between space and Earth, and try to lay the foundations for creating a global network of quantum communications. All of this explains in part why the European Union will launch a €1 billion funded “flagship” project in 2018 to boost quantum technologies.
"The Chinese quantum satellite has the potential to show that such technology can be applied on a global scale," said Félix Bussières , a quantum technology expert at the University of Geneva, Switzerland. “If they succeed, I think they would cause a great scientific and technological impact: in the future, they would help create a totally secure and undecipherable global communication network.” A new internet that is “hacker-proof”.
The new network
At least that is the objective of the QUESS mission, which in two years will try to create an intruder-proof network with a satellite and several ground bases capable of sharing quantum information, even using teleportation. The great advantage of this communication, based on the so-called quantum cryptography, and which already works on the ground in fiber optic cables through which photons circulate, is that any attempt to intercept the information is not only detected, but is useless. : It is totally impossible to understand a quantum message without having a key to read the data.
As Juan José García Ripoll , a researcher at the Institute of Fundamental Physics (IFF-CSIC), in Madrid, has explained, the basis of this communication system is similar to the one used by some heads of state during the Second World War. They recorded their spoken messages and mixed them with a source of white noise, so that only those who received the data from that noise could remove this distortion from the message and hear the words clearly. For whoever intercepted the message and did not have the key, the broadcast would be nothing more than meaningless noise.
"Many companies already sell quantum cryptography devices. In China there are also networks of this type to connect banks or government institutions" said this researcher. "The problem is that these fiber optic systems only work over distances of tens of kilometers. But with the satellite, this distance could be increased." While on the ground there is a lot of interference due to the absorption of light in the optical fiber or by other particles, in space the "noise" that can interfere with photons is less. In fact, the QUESS mission intends to test quantum communications at a distance of 1,200 kilometers, when today the record on land is 300.
But what role does teleportation play in quantum cryptography? As Félix Bussières explained, its role is to "increase the reach of cryptography and communication, and function as a tool for the future of communication."
Quantum computers
In addition, as Germán Sierra Rodero , research professor at the UAM-CSIC Institute of Theoretical Physics, has suggested, "teleportation will be one of the protocols that will form part of a quantum computer and that will allow information to be carried from one place to another" . In fact, for more than 15 years it has been considered that one of the means to reliably transmit the unstable quantum data inside one of these computers is to use quantum teleportation.
The great advantage of these quantum computers , as Bussières has explained, is that they have great computing power with large numbers , which is used to simulate complex chemical reactions, optimize industrial processes or synthesize better medicines. Also, they can do it very quickly. According to the Chinese scientists involved in QUESS, the problems that one of the most powerful supercomputers, such as the Tianhe-2, would solve in 100 years, could be processed by a quantum computer in just 0.01 seconds.
Be that as it may, the quantum future seems inevitable. Many scientists warn that it is a matter of time before Internet security systems , already unsafe, end up being cracked . More when quantum computers are developed, characterized by their great capacity. For this reason, the development of quantum cryptography is guaranteed, and the European Union already considers it an objective to improve the security systems of industry and infrastructures.
Apart from that, quantum technology is also applied to the field of metrology, to develop ever more precise atomic clocks, as well as to build much more sensitive sensors. Even in the field of astronomy, the idea of using this technology to connect several telescopes and create instruments with unprecedented resolution is raised. As impossible as it may seem, the quantum world threatens to be more and more present in everyday technology.
Science or fiction?
-Is it possible to teleport people?
No, quantum teleportation is just a way of transporting information, not matter. Such information is properties, such as the polarization of light, or the state of an atom, that are teleported between objects that already exist at two widely separated points in space.
Therefore, even if all the information that gives rise to a person could be teleported, we would first have to have a copy of all the atoms that make up that person at another point in space, something that is not feasible. Also, the quantum state of each of a person's atoms is constantly changing, but the person remains the same. Therefore, transferring quantum states does not imply transferring a person.
-And can you teleport at least objects?
In theory, quantum information could be teleported from macroscopic objects, but to achieve this, the objects must have a pure quantum state, a very fragile and ephemeral situation that depends on the environment not interacting with them. Experiments with larger atoms and molecules make it much easier to disturb this quantum state, because other atoms or weaker thermal radiation can deflect them from this state. This is the reason why in the everyday and macroscopic world people do not perceive the quantum effects that small particles do suffer.
"And what about teleportation through time?"
The only way to travel through time contemplated by scientific theory is to go through a wormhole, or Einstein-Rosen bridge.
-So, what is quantum teleportation for?
It is a developing field within quantum mechanics that could be used to create totally indecipherable communication systems over long distances. It will also serve to facilitate the development of quantum computers, devices much more powerful than the best current supercomputers. In addition, work is being done to design much more sensitive telescopes and sensors than the current ones.
-And how it works? (By Juan José García Ripoll, IFF physicist)
Teleportation works through entanglement , a feature of quantum mechanics whereby two particles "coordinate" or correlate their quantum states so that the value of any property, such as the polarization or color of a photon, is the same for each other. both particles. This would be of little interest were it not for the fact that in the quantum world these properties can be in an "undefined" state, a random superposition of many possibilities that is only resolved at the moment we look at the particle.
How is teleportation used in practice? Suppose in the vignette Bob wants to ask Alicia to marry him, but he doesn't want anyone else to know the answer. Bob starts by creating a pair of entangled photons: he keeps one in a "box" and sends the other to Alice. Alice takes that second photon and puts it in contact with another photon or an atom where she has saved the answer (0 for no and 1 for yes). When these two particles interact, it happens that instantly both Alice's photon and Bob's photon change randomly. Alice's photon will contain a random value, say 0 or 1, and Bob's will contain another random value, also 0 or 1. If Alice sends her values to Bob, Bob can combine them with her value to get the answer, "yes." or not".
There are therefore two important points in teleportation: First, the state of two distant particles changes instantly. This happens because the statistical indefiniteness that existed when creating the entangled photons disappears when Alice acts on them.
The second important point is that Alice and Bob in the end only have noise and can only reconstruct the information when one sends his part of the data to the other. However, this communication is secure, because the information Alice sends to Bob is completely random and independent of his answer, "yes" or "no."