Future teleportation is only the first stage of a whole series of experiments.

Vladivostok, IA Primorye24. Next summer, Chinese scientists are planning to conduct the world's first quantum teleportation experiment, Versiya reports.

The declared distance over which the particles will move is 1200 kilometers. Nature News tells about the plans of scientists from the Celestial Empire. It is known that as part of the test, specialists will launch a near-Earth satellite in June this year. It will act as a link between the two earth stations. It is known that experts plan to send particles from China to Vienna. Before launching the so-called "teleport", scientists are going to find out how reliable the cryptographic connection between cities is. The satellite will act as a teleporter - it is he who will carry out the contactless movement of photons. The distance between stations in Europe and China is more than 1200 kilometers. The success of the test, according to scientists, is beyond doubt. The fact that quantum teleportation can be carried out over any, including the largest distances, became known back in the middle of the last century.

According to physicists, the future teleportation of particles from China to Europe by satellite is only the first stage of a whole series of experiments. In the future, scientists plan to conduct a similar experiment with the participation of stations on the satellite, the Earth and the Moon. The process of quantum teleportation is the transfer of the quantum state of certain particles to any distance. For its implementation, specialists take a paired quantum particle and divide it into shares. According to the rules of quantum mechanics, in the case of separation of paired particles from each other, each of the shares retains information about its partner. A similar study has already been carried out by employees of an American university. They managed to carry out quantum teleportation for 102 kilometers. To carry out the process, experts used not a satellite, but an optical fiber. Despite the fact that the paired photons were separated by more than a hundred kilometers, a change in the state of one of them affected the other

She conducted a satellite experiment on the transfer of quantum states between pairs of entangled photons (the so-called quantum teleportation) over a record distance of more than 1200 km.

The phenomenon (or entanglement) arises when the states of two or more particles are interdependent (correlated), which can be separated over arbitrarily long distances, but at the same time they continue to “feel” each other. The measurement of the parameter of one particle leads to the instant destruction of the entangled state of the other, which is difficult to imagine without understanding the principles of quantum mechanics, especially since the particles (it was specially shown in experiments to violate the so-called Bell inequalities) do not have any hidden parameters that would store information about the state of the “companion”, and at the same time, an instantaneous state change does not lead to a violation of the causality principle and does not allow useful information to be transmitted in this way.

To transmit real information, the participation of particles moving at a speed not exceeding the speed of light is additionally necessary. For example, photons having a common progenitor can act as entangled particles, and, say, their spin is used as a dependent parameter.

The transfer of states of entangled particles over increasingly long distances and under the most extreme conditions is of interest not only to scientists involved in fundamental physics, but also to engineers designing secure communications. It is believed that the phenomenon of entanglement of particles in the future will provide us with, in principle, unhackable communication channels. "Protection" in this case will be the inevitable notification of the participants in the conversation that someone else has interfered in their connection.

Evidence of this will be the unbreakable laws of physics - the irreversible collapse of the wave function.

Prototypes of devices for implementing such secure quantum communication have already been created, but there are also ideas to compromise the operation of all these “absolutely secure channels”, for example, by reversible weak quantum measurements, so it is still unclear whether quantum cryptography will be able to get out of the prototype testing stage, not whether all developments will be doomed in advance and unsuitable for practical application.

Another point: the transmission of entangled states has so far only been carried out over distances not exceeding 100 km, due to photon losses in the optical fiber or in air, since the probability that at least some of the photons will reach the detector becomes vanishingly small. From time to time there are reports of another achievement on this path, but it is not yet possible to cover the entire globe with such a connection.

So, earlier this month, Canadian physicists announced successful attempts to communicate via a secure quantum channel with an aircraft, but it was only 3-10 km from the transmitter.

The so-called quantum repeater protocol is recognized as one of the ways to radically improve signal propagation, but its practical value remains in question due to the need to solve a number of complex technical issues.

Another approach is precisely to use satellite technology, since the satellite can remain in line of sight at the same time for different very distant places on Earth. The main advantage of this approach may be that most of the photon path will be in almost vacuum with almost zero absorption and the elimination of decoherence (coherence violation due to the interaction of particles with the environment).

To demonstrate the feasibility of satellite experiments, Chinese experts conducted preliminary ground-based tests that demonstrated successful bidirectional propagation of entangled photon pairs through an open environment at distances of 600 m, 13 km and 102 km with an effective channel loss of 80 dB. Experiments were also carried out on the transfer of quantum states on moving platforms under conditions of high losses and turbulence.

After detailed feasibility studies with the participation of Austrian scientists, a $ 100 million satellite was developed, launched on August 16, 2016 from the Jiuquan Cosmodrome in the Gobi Desert using the Long March 2D launch vehicle into an orbit with an altitude of 500 km.

The satellite was named "Mo-tzu" in honor of the ancient Chinese philosopher of the 5th century BC, the founder of Moism (the doctrine of universal love and state consequentialism). For several centuries in China, Mohism successfully competed with Confucianism, until the latter was adopted as the state ideology.

The Mozi mission is supported by three ground stations: in Delinghe (Qinghai Province), Nanshan in Urumqi (Xinjiang) and the GaoMeiGu Observatory (GMG) in Lijiang (Yunnan Province). The distance between Delinghe and Lijiang is 1203 km. The distance between the orbiting satellite and these ground stations varies between 500-2000 km.

Because entangled photons cannot simply be "amplified" like classical signals, new methods had to be developed to reduce attenuation in the transmission channels between Earth and satellites. To achieve the desired coupling efficiency, it was necessary to simultaneously achieve the minimum beam divergence and high-speed and high-precision pointing to the detectors.

Having developed an ultra-bright cosmic source of two-photon entanglement and high-precision APT (acquiring, pointing, and tracking) technology, the group established a “quantum coupling” between pairs of photons separated by 1203 km, scientists conducted the so-called Bell test to check for violations of locality (the ability to instantly affect the state of a remote particles) and obtained a result with a statistical significance of four sigma (standard deviations).

Scheme of the photon source on the satellite. The thickness of the KTiOPO4 (PPKTP) crystal is 15 mm. A pair of off-axis concave mirrors focuses the pump laser (PL) at the center of the PPKTP crystal. The output of the Sagnac interferometer uses two dichromatic mirrors (DM) and filters to separate the signal photons from the pump laser. Two additional mirrors (PI) remotely controlled from the ground are used to fine-tune the beam direction for optimal beam collection efficiency. QWP - quarter-wave phase section; HWP - half-wave phase section; PBS - polarizing beam splitter.

Compared to previous methods using the most common commercial samples of telecommunications fiber, the efficiency of a satellite connection turned out to be many orders of magnitude higher, which, according to the authors of the study, opens the way for practical applications previously unavailable on Earth.

MOSCOW, July 12 - RIA Novosti. Physicists in Shanghai claim to have successfully carried out the first "cosmic" quantum teleportation by relaying information about the state of a particle from the Mo Tzu quantum satellite to a tracking station on Earth, according to an article posted in the electronic library arXiv.org

“We announce the first quantum teleportation of single photons from an observatory on Earth to a satellite in near-Earth orbit, 1,400 kilometers away from it. The successful implementation of this task paves the way for ultra-long-range teleportation and is the first step towards creating a quantum Internet,” write Jian -Wei Pan (Jian-Wei Pan) from the University of Shanghai and his colleagues.

The phenomenon of quantum entanglement is the basis of modern quantum technologies. This phenomenon, in particular, plays an important role in secure quantum communication systems - such systems completely exclude the possibility of imperceptible "wiretapping" due to the fact that the laws of quantum mechanics prohibit "cloning" of the state of light particles. At present, quantum communication systems are being actively developed in Europe, China, and the USA.

In recent years, scientists from Russia and foreign countries have created dozens of quantum communication systems, the nodes of which can exchange data over fairly large distances, which are about 200-300 kilometers. All attempts to expand these networks to the international and intercontinental level have encountered insurmountable difficulties related to the way light is attenuated when traveling through optical fiber.

For this reason, many teams of scientists have thought about transferring quantum communication systems to the "cosmic" level, exchanging information via satellite, allowing you to restore or strengthen the "invisible connection" between entangled photons. The first spacecraft of its kind is already in orbit - it is the Chinese satellite Mo Tzu, launched into space in August 2016.

This week, Pan and his colleagues reported on the first successful quantum teleportation experiments carried out aboard the Mo-Tzu and at a communications station in Ngari, Tibet, built at an altitude of four kilometers to communicate with the first quantum satellite.

Quantum teleportation was first described at a theoretical level in 1993 by a group of physicists led by Charles Bennett. According to their idea, atoms or photons can exchange information at any distance if they were "entangled" at the quantum level.

To carry out this process, a conventional communication channel is required, without which we cannot read the state of entangled particles, which is why such "teleportation" cannot be used to transmit data over astronomical distances. Despite this limitation, quantum teleportation is of great interest to physicists and engineers because it can be used to transmit data in quantum computers and to encrypt data.

Guided by this idea, the scientists entangled two pairs of photons in the laboratory in Ngari, and transmitted one of the four "entangled" particles aboard the Mo-Tzu using a laser. The satellite simultaneously measured the state of both this particle and another photon that was on board at that moment, as a result of which information about the properties of the second particle was instantly "teleported" to the Earth, changing the behavior of the "ground" photon entangled with the first particle.

In total, as Chinese physicists say, they managed to "entangle" and teleport over 900 photons, which confirmed the correctness of the "Mo-Dzy" and proved that two-way "orbital" quantum teleportation is possible in principle. In a similar way, as scientists note, it is possible to transmit not only photons, but also qubits, memory cells of a quantum computer, and other objects of the quantum world.

Last year, a Long March 2D rocket took off from the Gobi Desert and put the Mo Tzu satellite into orbit in synchronism with the Sun, so it makes its way around the Earth every day. Mo Tzu is a highly sensitive satellite designed to transmit quantum information. It can detect the quantum states of individual photons released from the surface of our planet.

Today, the Mo Tzu team announced their unique achievement: they have succeeded in creating the first ground-to-ground satellite quantum network. This network was used to teleport the first object in history from Earth into its orbit. Teleportation is carried out by scientists who have conducted experiments in the field of optical physics. This process is based on the strange phenomenon of entanglement, during which two photons form a single point in time and space. From a technical point of view, they are described by a single wave function.

A feature of quantum entanglement is that these two photons exist at the same point, even if there are kilometers between them. Thus, a change in the state of one instantly affects the state of the other. Back in the 90s of the last century, scientists realized that they could use this phenomenon to teleport objects from one point of the Universe to another.

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The idea is to "load" information into one photon, then the other becomes identical to the first. This is teleportation

Such experiments have been carried out many times in laboratory conditions on Earth, but this is the first time they have been tested in interstellar space. Teleportation is of great importance for a whole range of technologies related to quantum networks and computing.

In fact, there is no maximum distance for teleportation of photons, but the connection created between them is too fragile and can be destroyed due to foreign matter that has appeared in the atmosphere or in the optical fiber. To confirm their theory, scientists conducted experiments all the time at a greater distance, and now they went into orbit. True, for this it was necessary to build a station in Tibet at an altitude of 4 thousand meters.

As part of the experiment, entangled pairs of photons were created, which were launched at a speed of 4000 m/s