Such a teleport machine was built in the film "Contact". With her help, the heroine Jodie Foster traveled to another world, or maybe not ...

In fantasy worlds invented by writers and screenwriters, teleportation has long been a standard transport service. It seems difficult to find such a fast, convenient and at the same time intuitive way to move in space.

beautiful idea scientists also support teleportation: even the founder of cybernetics, Norbert Wiener, in his work “Cybernetics and Society” devoted an entire chapter to “the possibility of traveling by telegraph”. Half a century has passed since then, and during this time we have come close to humanity's dream of such travel: successful quantum teleportation has been carried out in several laboratories around the world.

Basics

Why teleportation is quantum? The fact is that quantum objects (elementary particles or atoms) have specific properties that are determined by the laws of the quantum world and are not observed in the macrocosm. It is these properties of particles that served as the basis for experiments on teleportation.

EPR paradox

During the period of active development quantum theory, in 1935, in the famous work of Albert Einstein, Boris Podolsky and Nathan Rosen "Can a quantum mechanical description of reality be complete?" the so-called EPR paradox (the Einstein-Podolsky-Rosen paradox) was formulated.

The authors showed that it follows from quantum theory that if there are two particles A and B with a common past (those scattered after a collision or formed during the decay of some particle), then the state of particle B depends on the state of particle A, and this dependence should manifest itself instantly and at any distance . Such particles are called an EPR pair and are said to be in an "entangled" state.

First of all, let us recall that in the quantum world a particle is a probabilistic object, that is, it can be in several states at the same time - for example, it can be not just “black” or “white”, but “gray”. However, when measuring such a particle, we will always see only one of the possible states - "black" or "white", and with a certain predictable probability, and all other states will be destroyed. Moreover, from two quantum particles it is possible to create such an “entangled” state that everything will be even more interesting: if one of them turns out to be “black” when measured, then the other will certainly be “white”, and vice versa!

To understand what the paradox is, let's first conduct an experiment with macroscopic objects. Let's take two boxes, each of which contains two balls - black and white. And we will take one of these boxes to the North Pole, and the other to the South.

If we take out one of the balls at the South Pole (for example, black), then this will not affect the result of the choice at the North Pole. It is not at all necessary that in this case we will come across a white ball there. This simple example confirms that it is impossible to observe the EPR paradox in our world.

But in 1980, Alan Aspect experimentally showed that the EPR paradox does exist in the quantum world. Special measurements of the state of EPR particles A and B showed that the EPR pair is not just connected by a common past, but particle B somehow instantly “knows” how particle A was measured (what its characteristic was measured) and what the result was . If we were talking about the boxes with four balls mentioned above, then this would mean that having taken out a black ball at the South Pole, we must certainly take out a white one at the North Pole! But there is no interaction between A and B, and superluminal signal transmission is impossible! In subsequent experiments, the existence of the EPR paradox was confirmed even if the particles of the EPR pair were separated from each other by a distance of about 10 km.

These absolutely incredible experiences from the point of view of our intuition are easily explained by quantum theory. After all, an EPR pair just represents two particles in an “entangled” state, which means that the measurement result, for example, of particle A determines the measurement result of particle B.

It is interesting that Einstein considered the behavior of particles in EPR pairs predicted by him to be “the action of demons at a distance” and was sure that the EPR paradox once again demonstrates the inconsistency of quantum mechanics, which the scientist refused to accept. He believed that the explanation of the paradox is unconvincing, because "if, according to quantum theory, the observer creates or can partially create the observed, then the mouse can remake the Universe simply by looking at it."

Teleportation experiments

In 1993, Charles Bennett and his colleagues figured out how to use the wonderful properties of EPR pairs: they invented a way to transfer the quantum state of an object to another quantum object using an EPR pair and called this method quantum teleportation. And in 1997, a group of experimenters led by Anton Zeilinger for the first time carried out quantum teleportation of the state of a photon. The teleportation scheme is described in detail in the sidebar.

Limitations and frustrations

It is fundamentally important that quantum teleportation is not a transfer of an object, but only an unknown quantum state of one object to another quantum object. Not only does the quantum state of the teleported object remain a mystery to us, it is also irreversibly destroyed. But what we can be quite sure of is that we got the identical state of another object elsewhere.

Those who expected teleportation to be instantaneous will be disappointed. In the Bennett method, successful teleportation requires a classical communication channel, which means that the teleportation speed cannot exceed the data transfer rate over a conventional channel.

And it is still completely unknown whether it will be possible to switch from the teleportation of the states of particles and atoms to the teleportation of macroscopic objects.

Application

A practical application for quantum teleportation was quickly found - these are quantum computers, where information is stored in the form of a set of quantum states. Here, quantum teleportation turned out to be an ideal way to transfer data, which fundamentally excludes the possibility of intercepting and copying the transmitted information.

Will it be the man's turn?

Despite all the modern achievements in the field of quantum teleportation, the prospects for human teleportation remain very vague. Of course, I want to believe that scientists will come up with something. Back in 1966, Stanislav Lem wrote in his book The Sum of Technology: “If we succeed in synthesizing Napoleon from atoms (provided that we have at our disposal his “atom-by-atom inventory”), then Napoleon will be a living person. If you take a similar inventory from any person and transfer it “by telegraph” to a receiving device, the equipment of which, based on the received information, will recreate the body and brain of this person, then he will leave the receiving device alive and healthy.

However, practice in this case is much more complicated than theory. So you and I are unlikely to have to travel the worlds with the help of teleportation, and even more so with guaranteed safety, because one mistake is enough and you can turn into a meaningless set of atoms. Here is an experienced galactic inspector from the novel by Clifford Simak knows a lot about this and not in vain believes that "those who undertake to transfer matter over a distance should first learn how to do it properly."

Quantum teleportation is one of the most important protocols in quantum information. Based on the physical resource of entanglement, it serves as the main element of various information tasks and is an important constituent part quantum technologies playing a key role in further development quantum computing, networks and communication.

From science fiction to the discovery of scientists

More than two decades have passed since the discovery of quantum teleportation, which is perhaps one of the most interesting and exciting consequences of the “weirdness” of quantum mechanics. Before these great discoveries were made, this idea belonged to the field science fiction. First coined in 1931 by Charles H. Fort, the term "teleportation" has since been used to refer to the process by which bodies and objects are transferred from one place to another without actually traveling the distance between them.

In 1993, an article was published describing a quantum information protocol called "quantum teleportation" that shared several of the features listed above. In it, the unknown state of a physical system is measured and subsequently reproduced or "reassembled" at a remote location (the physical elements of the original system remain at the transmission site). This process requires classical means of communication and excludes FTL communication. It needs a resource of entanglement. In fact, teleportation can be seen as the quantum information protocol that most clearly demonstrates the nature of entanglement: without its presence, such a state of transmission would not be possible within the framework of the laws that describe quantum mechanics.

Teleportation plays an active role in the development of information science. On the one hand, a protocol that plays a decisive role in the development of formal quantum information theory, and on the other hand, it is a fundamental component of many technologies. Quantum repeater - key element communications over long distances. Quantum switch teleportation, dimension-based computing, and quantum networks are all derivatives of it. It is also used as a simple tool to study "extreme" physics concerning time curves and evaporation

Today, quantum teleportation has been validated in laboratories around the world using many different substrates and technologies, including photonic qubits, nuclear magnetic resonance, optical modes, groups of atoms, trapped atoms, and semiconductor systems. Outstanding results have been achieved in the field of teleportation range, experiments with satellites are coming. In addition, attempts have begun to scale up to more complex systems.

Teleportation of qubits

Quantum teleportation was first described for two-level systems, the so-called qubits. The protocol considers two distant parties, called Alice and Bob, who share 2 qubits, A and B, in a pure entangled state, also called a Bell pair. At the input, Alice is given another qubit a, whose state ρ is unknown. She then performs a joint quantum measurement called Bell detection. It takes a and A to one of the four Bell states. As a result, the state of Alice's input qubit disappears during the measurement, while Bob's qubit B is simultaneously projected onto Р † k ρP k . At the last stage of the protocol, Alice sends the classical result of her measurement to Bob, who uses the Pauli operator P k to restore the original ρ.

The initial state of Alice's qubit is considered unknown, since otherwise the protocol is reduced to its remote measurement. Alternatively, it may itself be part of a larger composite system shared with a third party (in which case successful teleportation requires reproducing all correlations with that third party).

A typical quantum teleportation experiment assumes an initial state that is pure and belonging to a limited alphabet, such as the six poles of a Bloch sphere. In the presence of decoherence, the quality of the reconstructed state can be quantified by the teleportation accuracy F ∈ . This is the accuracy between the states of Alice and Bob, averaged over all of the Bell detection results and the original alphabet. At low accuracy values, there are methods that allow imperfect teleportation without using an obfuscated resource. For example, Alice can directly measure her initial state by sending the results to Bob to prepare the resulting state. This measurement-preparation strategy is called "classical teleportation". She has maximum precision F class = 2/3 for an arbitrary input state, which is equivalent to an alphabet of mutually unbiased states, such as the six poles of a Bloch sphere.

Thus, a clear indication of the use of quantum resources is the accuracy value F> F class .

Not a single qubit

According to teleportation is not limited to qubits, it can include multidimensional systems. For each finite dimension d, one can formulate an ideal teleportation scheme using a basis of maximally entangled state vectors, which can be obtained from a given maximally entangled state and a basis (U k ) of unitary operators satisfying tr(U † j U k) = dδ j,k . Such a protocol can be constructed for any finite-dimensional Hilbert space, the so-called. discrete variable systems.

In addition, quantum teleportation can also be extended to systems with an infinite-dimensional Hilbert space, called continuous-variable systems. As a rule, they are implemented by optical bosonic modes whose electric field can be described by quadrature operators.

Velocity and the Uncertainty Principle

What is the speed of quantum teleportation? Information is transmitted at a rate similar to that of the same amount of classical data - perhaps co. Theoretically, it can be used in ways that classical cannot - for example, in quantum computing, where the data is available only to the recipient.

Does Quantum Teleportation Violate In the past, the idea of ​​teleportation was not taken very seriously by scientists because it was thought to violate the principle that no measuring or scanning process could extract all the information of an atom or other object. According to the uncertainty principle, the more precisely an object is scanned, the more it is affected by the scanning process, until a point is reached where the original state of the object is violated to such an extent that it is no longer possible to obtain enough information to create an exact copy. This sounds convincing: if a person cannot extract information from an object to create a perfect copy, then the last one cannot be made.

Quantum teleportation for dummies

But six scientists (Gilles Brassard, Claude Crepeau, Richard Josa, Asher Perez, and William Wouters) have found a way around this logic by exploiting the famous and paradoxical feature of quantum mechanics known as the Einstein-Podolsky-Rosen effect. They found a way to scan part of the information of the teleported object A, and transfer the rest of the unverified part through the mentioned effect to another object C, which had never been in contact with A.

In the future, by applying to C an influence that depends on the scanned information, you can put C into state A before scanning. A itself is no longer in the same state, as it has been completely changed by the scanning process, so what has been achieved is teleportation, not replication.

Fight for distance

• The first quantum teleportation was carried out in 1997 almost simultaneously by scientists from the University of Innsbruck and the University of Rome. During the experiment, the original photon, which has a polarization, and one of the pair of entangled photons, were changed in such a way that the second photon received the polarization of the original one. In this case, both photons were at a distance from each other.
• In 2012, another quantum teleportation took place (China, University of Science and Technology) through a high mountain lake at a distance of 97 km. A team of scientists from Shanghai, led by Huang Yin, managed to develop a homing mechanism that made it possible to accurately aim the beam.
• In September of the same year, a record quantum teleportation of 143 km was carried out. Austrian scientists from the Austrian Academy of Sciences and the University of Vienna, led by Anton Zeilinger, have successfully transferred quantum states between the two Canary Islands of La Palma and Tenerife. The experiment used two optical communication lines in open space, quantum and classical, frequency uncorrelated polarization entangled pair of source photons, ultra-low noise single-photon detectors and coupled clock synchronization.
• In 2015, researchers from the US National Institute of Standards and Technology for the first time transmitted information over a distance of more than 100 km via optical fiber. This became possible thanks to the single-photon detectors created at the institute, using superconducting nanowires made of molybdenum silicide.

It is clear that the ideal quantum system or technology does not yet exist and the great discoveries of the future are yet to come. Nevertheless, one can try to identify possible candidates in specific applications of teleportation. Suitable hybridization of these, given a compatible framework and methods, may provide the most promising future for quantum teleportation and its applications.

short distances

Teleportation over short distances (up to 1 m) as a quantum computing subsystem is promising for semiconductor devices, the best of which is the QED scheme. In particular, superconducting transmon qubits can guarantee deterministic and high-precision on-chip teleportation. They also allow real-time direct feed, which looks problematic on photonic chips. In addition, they provide a more scalable architecture and better integration of existing technologies compared to previous approaches such as trapped ions. At present, the only drawback of these systems seems to be their limited coherence time (<100 мкс). Эта проблема может быть решена с помощью интегрирования схемы QED с полупроводниковыми спин-ансамблевыми ячейками памяти (с азотно-замещенными вакансиями или легированными редкоземельными элементами кристаллами), которые могут обеспечить длительное время когерентности для квантового хранения данных. В настоящее время данная реализация является предметом приложения больших усилий научного сообщества.

City connection

Teleportation communication on a city scale (several kilometers) could be developed using optical modes. With sufficiently low losses, these systems provide high speeds and bandwidth. They can be extended from desktop implementations to medium-range systems operating over the air or fiber, with possible integration with ensemble quantum memory. Longer distances but lower speeds can be achieved with a hybrid approach or by developing good repeaters based on non-Gaussian processes.

Long distance communication

Long-distance quantum teleportation (over 100 km) is an active area, but still suffers from an open problem. Polarization qubits are the best vehicles for low speed teleportation over long fiber optic links and over the air, but the protocol is currently probabilistic due to Bell's incomplete detection.

Although probabilistic teleportation and entanglements are acceptable for problems such as entanglement distillation and quantum cryptography, this is clearly different from communication, in which the input information must be completely preserved.

If we accept this probabilistic nature, then satellite implementations are within the reach of current technologies. In addition to the integration of tracking methods, the main problem is high losses caused by beam spreading. This can be overcome in a configuration where entanglement is distributed from the satellite to large aperture ground-based telescopes. Assuming a satellite aperture of 20 cm at 600 km altitude and a 1 m telescope aperture on the ground, about 75 dB of downlink loss can be expected, which is less than the 80 dB loss at ground level. Ground-to-satellite or satellite-to-satellite implementations are more complex.

quantum memory

The future use of teleportation as part of a scalable network directly depends on its integration with quantum memory. The latter should have an excellent radiation-to-matter interface in terms of conversion efficiency, recording and reading accuracy, storage time and bandwidth, high speed and storage capacity. First of all, this will allow the use of repeaters to extend communication far beyond direct transmission using error correction codes. The development of a good quantum memory would allow not only to distribute entanglement over the network and teleportation communication, but also to process the stored information in a coherent manner. Ultimately, this could turn the network into a globally distributed one or the basis for a future quantum internet.

Promising developments

Atomic ensembles have traditionally been considered attractive due to their efficient light-to-matter conversion and their millisecond lifetimes, which can be as high as the 100ms required to transmit light on a global scale. However, more promising developments today are expected based on semiconductor systems, where excellent spin-ensemble quantum memory is directly integrated with the scalable QED circuit architecture. This memory can not only extend the coherence time of the QED circuit, but also provide an optical-microwave interface for the interconversion of optical-telecom and chip microwave photons.

Thus, the future discoveries of scientists in the field of the quantum Internet are likely to be based on long-range optical communication coupled with semiconductor nodes for processing quantum information.

quantum teleportation- this is teleportation not of physical objects, not of energy, but of a state. But in this case, the states are transferred in a way that is impossible to do in the classical view. As a rule, a large number of comprehensive measurements are required to transmit information about an object. But they destroy the quantum state, and we have no way to re-measure it. Quantum teleportation is used in order to transfer, transfer a certain state, having minimal information about it, without "looking" into it, without measuring it, and thereby without violating it.

qubits

This is an example of obtaining information in the classical way. Having received a large amount of data, the addressee can recreate this state. However, quantum mechanics allows us not to prepare many states. Imagine that we have only one, unique, and there is no other like it. Then in the classics it will no longer be possible to convey it. Physically, directly, this is also not always possible. And in quantum mechanics, we can use the effect of entanglement.

We also use the phenomenon of quantum nonlocality, that is, a phenomenon that is impossible in the world familiar to us, in order for this state to disappear here and appear there. Moreover, the most interesting thing is that in relation to the same quantum objects there is a non-cloning theorem. That is, it is impossible to create a second identical state. One must be destroyed in order for the other to appear.

quantum entanglement

The quantum case is different in that the state that came to me before the measurement is neither blue nor green - it is in a superposition of blue and green. After you have separated the shoes, the result is already predetermined. While the bags are being carried, they have not yet been opened, but it is already clear what will be there. And while quantum objects are not measured, nothing has been decided yet.

If we take not color, but polarization, that is, the direction of electric field oscillations, two options can be distinguished: vertical and horizontal polarization and +45 ° - -45 °. If you add together the horizontal and vertical in equal proportion, you get +45 °, if you subtract one from the other, then -45 °. Now let's imagine that in the same way one photon hit me and the other one hit you. I looked: it is vertical. So you are horizontal. Now let's imagine that I saw a vertical one, and you looked at it in a diagonal basis, that is, you looked - it is +45 ° or -45 °, you will see either outcome with equal probability. But if I looked in the diagonal basis and saw +45°, then I know for sure that you have -45°.

Einstein-Podolsky-Rosen paradox

But in fact, this does not violate the theory of relativity, because we still cannot transmit information using this effect. Either a vertical or horizontal photon is measured. But it is not known in advance what it will be. Despite the fact that information cannot be transmitted faster than the speed of light, entanglement allows the quantum teleportation protocol to be implemented. What is it? An entangled pair of photons is born. One goes to the transmitter, the other - to the receiver. The transmitter jointly measures the target photon it is to transmit. And with a probability of ¼ he will get an OK result. He can report this to the receiver, and the receiver at that moment will know that he has exactly the same condition as the transmitter had. And with a probability of ¾, he gets a different result - not exactly an unsuccessful measurement, but just a different result. But in any case, this is useful information that can be passed on to the recipient. The receiver in three out of four cases must make an additional rotation of its qubit in order to receive the transmitted state. That is, 2 bits of information are transmitted, and with the help of them you can teleport a complex state that cannot be encoded by them.

quantum cryptography

This technology has one big drawback. The fact is that, as we said earlier, it is impossible to create a copy of a photon. A normal fiber signal can be amplified. For the quantum case, it is impossible to amplify the signal, since the amplification will be equivalent to some interceptor. In real life, on real lines, transmission is limited to a distance of approximately 100 kilometers. In 2016, the Russian Quantum Center held a demonstration on the lines of Gazprombank, where they showed quantum cryptography on 30 kilometers of fiber in an urban environment.

In the laboratory, we are able to show quantum teleportation at a distance of up to 327 kilometers. But, unfortunately, long distances are impractical, because photons are lost in the fiber and the speed is very low. What to do? You can put an intermediate server that will receive information, decrypt it, then encrypt it again and transmit further. This is what the Chinese do, for example, when building their quantum cryptography network. The same approach is used by the Americans.

Quantum teleportation in this case is a new method that allows solving the problem of quantum cryptography and increasing the distance to thousands of kilometers. And in this case, the same photon that is transmitted is repeatedly teleported. Many groups around the world are working on this task.

quantum memory

In quantum cryptography, this is a kind of way station. Such stations are called quantum repeaters, and they are now one of the main areas for research and experimentation. This is a popular topic, in the early 2010s, repeaters were a very distant prospect, but now the task looks feasible. Largely because technology is constantly evolving, including through telecommunications standards.

The course of the experiment in the laboratory

The initial state is prepared by the laser. To prepare entangled states, a nonlinear crystal is used, which is pumped by a pulsed or cw laser. Pairs of photons are produced due to non-linear effects. Imagine that we have a photon of energy two - ℏ(2ω), it is converted into two photons of energy one - ℏω + ℏω. These photons are born only together, one photon cannot be separated first, then another. And they are connected (entangled) and exhibit non-classical correlations.

History and current research

Quantum teleportation was proposed theoretically in 1993 by a group of American scientists led by Charles Bennett - then this term appeared. The first experimental implementation was carried out in 1997 by two groups of physicists at once in Innsbruck and Rome. Gradually, scientists managed to transmit states over an increasing distance - from one meter to hundreds of kilometers or more.

Now people are trying to make experiments that, perhaps in the future, will become the basis for quantum repeaters. It is expected that after 5–10 years we will see real quantum repeaters. The direction of state transfer between objects of different nature is also developing, including in May 2016 a hybrid quantum teleportation was carried out at the Quantum Center, in the laboratory of Alexander Lvovsky. The theory also does not stand still. In the same Quantum Center, under the leadership of Alexei Fedorov, a teleportation protocol is being developed not in one direction, but bidirectional, in order to teleport states simultaneously towards each other with the help of one pair.

As part of our work on quantum cryptography, we create a quantum distribution and key device, that is, we generate a key that cannot be intercepted. And then the user can encrypt information with this key using the so-called one-time pad. New advantages of quantum technologies should be revealed in the next decade. The creation of quantum sensors is being developed. Their essence is that due to quantum effects, we can measure, for example, a magnetic field, temperature much more accurately. That is, the so-called NV centers in diamonds are taken - these are tiny diamonds, they have nitrogen defects that behave like quantum objects. They are very similar to a frozen single atom. Looking at this defect, one can observe changes in temperature, and inside a single cell. That is, to measure not just the temperature under the arm, but the temperature of the organelle inside the cell.

Quantum mechanics has greatly changed human life. Semiconductors, the atomic bomb, nuclear energy - these are all objects that work thanks to it. The whole world is now struggling to begin to control the quantum properties of single particles, including entangled ones. For example, three particles participate in teleportation: one pair and the target. But each of them is controlled separately. Individual control of elementary particles opens up new horizons for technology, including the quantum computer.

Yuri Kurochkin, Candidate of Physical and Mathematical Sciences, Head of the Quantum Communications Laboratory of the Russian Quantum Center.

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At a distance of about 1200 kilometers - between earth and space! The researchers also plan to conduct similar experiments on quantum teleportation between the Earth and the Moon.

Teleportation ... A word from science fiction books, from stories about space adventures, where heroes overcome gigantic distances in seconds using a teleporter. Quantum teleportation has nothing to do with the actual movement of objects. In that case, what is it and why is it called that? About quantum teleportation AiF.ru told the head of the laboratory of physics of the Polytechnic Museum Yuri Mikhailovsky:

“You need to understand that with quantum teleportation, there is no movement of an object from one place in space to another, as with teleportation in the usual sense of the word. With the help of quantum teleportation, it is not the object itself that teleports, that is, it instantly moves, but the state of this object! Roughly speaking, we have a certain object that has a certain state, and with the help of quantum teleportation we can transfer this state to another place so that an object with the same properties appears there. (In China, the state of particles between two points on Earth will be transmitted using a space satellite, which is going to be put into orbit for the sake of this experiment - ed.) But about the object - conditionally. Let me explain: now we do not know how to transfer the state of complex objects. It is about conveying the state of individual atoms or photons, nothing more.

In order to implement quantum teleportation, you need to create a quantum entangled pair. For simplicity, we will talk about one state, the state of the spin of the particle. It can be in two states: spin up and spin down. We will try to convey these states. So, we are trying to create a so-called quantum entangled pair (usually a pair of light photons). It is arranged in such a way that their total spin is zero. That is, one photon has a spin up, the other has a spin down, when we create this pair, their sum is zero. At the same time, not only do we not know where the photons are looking, but the photons themselves do not know in which direction their spins are directed. They are in the so-called mixed state, indefinite. Maybe spin up, maybe down, no one knows until the act of measurement is done.

But we have a guarantee that if we measure one spin and it looks up, then the spin of the other photon looks down. Now let's take two entangled photons and spread them over a long distance, a kilometer, for example. And here we take one of the photons and measure its state. We determine that it has a spin up, and at this moment, at a distance of one kilometer, the spin of another mixed photon turns into a state with a spin down. By the act of measuring one photon, we changed the state of another photon.

Usually these two entangled photons are called Ansila and Bob.

This effect of quantum entanglement is used for teleportation. We have a spin that we would like to teleport, it is usually called Alice. So, the total spin of Alice and Ansila is measured, and at this moment Bob receives the state of Alice, or conjugate to it (opposite). About which one, we learn from the result of the measurement. After that, we need to transfer this information through the usual communication channel. Should Bob be turned over or not.

If, for example, we transmit the states of 10 spins, then to complete the teleportation, it is necessary to send a message like: “Change to opposite states 1, 3, 5, 6 and 8”.

This is how quantum teleportation works.

The Runet has never experienced such a thirst for knowledge in quantum mechanics as after the publication in the Kommersant newspaper of an article mentioning plans to introduce “teleportation” in Russia. The program of the Agency for Strategic Initiatives (ASI) for the technological development of Russia, however, is not limited to “teleportation”, however, it was this term that attracted the attention of social networks and the media and became the reason for many jokes.

Then the entangled particles are separated to the required distance - so that photons A and B remain in one place, and C in the other. A fiber optic cable is run between the two points. Note that the maximum distance at which quantum teleportation was carried out is already more than 100 km.

The task is to transfer the quantum state of an unentangled particle A to particle C. To do this, scientists measure the quantum property of photons A and B. The results of the measurements are then turned into a binary code that tells about the differences between particles A and B.

This code is then transmitted over the traditional communication channel, an optical fiber, and the recipient of the message on the other end of the cable, who possesses the C particle, uses this information as an instruction or key to manipulate the C particle - in essence, restoring the C particle to the state that the C particle had. particle A. As a result, particle C copies the quantum state of particle A - the information is teleported.

What is all this for?

First of all, quantum teleportation is planned to be used in quantum communication and quantum cryptography technologies - the security of this type of communication looks attractive for both business and the state, and the use of quantum teleportation makes it possible to avoid information loss when photons move along an optical fiber.

For example, recently it became known about the successful transfer of quantum information between two Gazprombank offices in Moscow via a 30.6-kilometer fiber optic. The project, on which the Russian Quantum Center (RKC) worked, and in which Gazprombank and the Ministry of Education and Science of the Russian Federation invested 450 million rubles, actually turned out to be the first “city” quantum communication line in Russia.

Another direction ˜ is quantum computers, where entangled particles can be used as qubits – units of quantum information.

Another idea is the "quantum internet": an entire network of communications based solely on quantum communication. To implement this concept, however, researchers need to “learn how to transfer quantum states between objects of different physical nature - photons, atoms, quantum dots, superconducting circuits, and so on,” said Alexander Lvovsky, an employee of the RCC and a professor at the University of Calgary, in a conversation with the N + 1 publication. .

Note that at the moment scientists are teleporting in the ground states of photons and atoms; larger objects have not yet been teleported.

Quantum teleportation as "the same" teleportation

Apparently, hypothetically, quantum teleportation can still be used to create copies of large objects, including humans - after all, the body also consists of atoms, the quantum states of which can be teleported. However, at the present stage of technological development, this is considered impossible and is attributed to the realm of fantasy.

“We are made up of oxygen, hydrogen and carbon, with a little bit of other chemical elements. If we collect the required number of atoms of the necessary elements, and then, using teleportation, bring them into a state identical to their state in the body of the teleported person, we will get the same person. It will be physically indistinguishable from the original except for its position in space (after all, identical quantum particles are indistinguishable). Of course, I am exaggerating to the utmost - a whole eternity separates us from human teleportation. However, the essence of the issue is precisely this: identical quantum particles are found everywhere, but it is not at all easy to bring them into the desired quantum state, ”said Alexander Lvovsky in an interview with N + 1.

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