MOSCOW, October 6 – Novosti, Nikolai Guryanov. Long-awaited and well-deserved – this is how the decision of the Nobel Committee in Physics is called this year. The main scientific award of the world was awarded to three scientists who created the foundation of the quantum era that humanity is entering. With a series of experiments, the laureates proved that Albert Einstein was wrong.
genius mistake
Ten million Swedish kronor, or about $900,000 at the current rate, will be shared by Frenchman Alain Aspe (75), American John Clauser (79) and Austrian Anton Zeilinger (77).
According to the official wording, the prize was awarded to them “for experiments with entangled photons, establishing violations of Bell’s inequalities, and pioneering quantum computer science.”
“We are already living in the quantum age. The Nobel Committee has confirmed the fundamental importance of our field of science,” says Igor Zakharov , senior researcher at the Skoltech Laboratory for Quantum Information Processing .
The founder of the theory of relativity made a great contribution to quantum mechanics with his theory of the photoelectric effect. In 1922, Einstein was awarded the highest scientific award for this work.
But he argued with the creators of quantum mechanics – Niels Bohr, Werner Heisenberg and others. In 1935, Einstein, together with Boris Podolsky and Nathan Rosen, published the article “Can we assume that the quantum mechanical description of physical reality is complete?”, formulating there the so-called EPR paradox (after the first letters of the names of the authors of this work).
CC0 / Paul Ehrenfest /
Niels Bohr with Albert Einstein at Paul Ehrenfest’s house in Leiden (December 1925)
“Imagine two particles (photons are usually considered) connected in a certain way. When they collide and then fly apart, the law of conservation of energy applies: if the spin (direction of rotation) of the first photon is directed in one direction, then the spin of the second is in the opposite direction. That is, the sum of their of rotation is zero. And if you measure a particle in one place, the result of measurements in another will be instantly known. This corresponds to classical physics. But in quantum physics, the property “direction of rotation” is fixed by measuring the first particle. The device can choose any direction of rotation. The second bound particle is magical somehow learns how the first one spins, and spins in the opposite direction. This is the EPR paradox,” says Zakharov.
The website of the Nobel Committee explains: entangled pairs can be compared to a machine that throws balls of different colors in opposite directions. When a boy catches a black ball, he immediately understands that the girl has caught a white one. According to classical physics, the balls have always been like this, and we simply eliminate our ignorance of their color. However, quantum mechanics says that the balls did not have a definite color until someone looked at them. Only then did one randomly turn white and the other black.
© THE ROYAL SWEDISH ACADEMY OF SCIENCES
Hidden variables and quantum mechanics
And how far two quanta are from each other does not matter.
“Einstein reasoned: if this is so, then we assume that the speed of light is not the main limitation on the speed of information transfer. He considered quantum mechanics to be incomplete. That is, it was necessary to find some hidden variables that determine the result of experiments,” Zakharov clarifies.
The quantum world has won
In 1964, Northern Irish physicist John Stuart Bell proved that there was a type of experiment that could determine whether a description of the world other than a purely quantum mechanical one was possible. If there are unknown variables, then such an experiment, repeated several times, will give a certain statistical value. This theorem is known as Bell’s inequalities.
“The experiments of the current Nobel laureates have shown that Bell’s inequalities are violated. The world is quantum, and we will have to live with it,” says Stanislav Straupe, head of the quantum computing sector of the Moscow State University’s Central Computer and Computer Institute.
The merit of John Clauser is that he was the first to conduct a realistic experiment that revealed a violation of Bell’s inequalities. In 1972, an American physicist built an apparatus that simultaneously emitted two entangled photons. Particles were directed at some angle to filters arranged like sunglasses: they blocked light polarized in a certain plane.
The photons were with parallel polarization, the direction of which was set using filters.
However, the experiment had a drawback: the filters were fixed. The observer could question the results: what if the setup had somehow chosen particles with a strong correlation and ignored the others?
© THE ROYAL SWEDISH ACADEMY OF SCIENCES
Schemes of experiments of Nobel laureates
Alain Aspe improved Clauser’s technique. He also registered those photons that did not pass through the filter. The French scientist sent particles to two filters set at different angles. The toggle switches set the direction for the photons after they had flown out of the source. This happened in billionths of a second, which ruled out even the theoretical possibility of falsifying the results. Thus, the “fullness” of quantum mechanics was proved.
The work of Anton Zeilinger opens the way to the practical application of knowledge about the properties of entangled particles.
“We cannot send a signal faster than the speed of light. Einstein is absolutely right here. But if we take care in advance to transmit bound particles over a long distance, we will be able to manipulate their state. The manipulation itself, or, as we say, teleportation, occurs instantly It really does not depend on the speed of light or any other restrictions,” Zakharov explains.
Quantum teleportation occurs when one of two entangled particles that have scattered in different directions meets and “entangles” with the third one. In this case, the first particle, left alone, acquires the properties of the third – and that, in turn, loses its identity. Zeilinger and his colleagues first performed such an experiment in 1997. Later, the scientist practiced the transmission of quantum information via fiber optic and satellite communications.
Quantum mechanics in the national economy
Communication systems are the most promising field of application of quantum technologies.
“Signals are encoded into single quantum objects, such as photons of light. This ensures that any interference in the process of information transmission will not go unnoticed. Thus, it is possible to create systems in which information is obviously protected,” says Alexey Fedorov.
Government structures are interested in these technologies. There is also commercial potential.
“Quantum communication is already working quite successfully, there are appropriate devices. Now the problem is in economic feasibility. It does not make sense for all applications to switch to more expensive technology – only for the most critical ones. And the question is how quickly it will be possible to reduce its cost so that it receives wider distribution. Devices are produced by several companies, including in Russia,” Straupe notes.
Zakharov adds that large amounts of data will not be sent via quantum communication. “They will transmit the key. Let’s say a thousand bytes. And the rest – whatever you like, the information cannot be disclosed without the key. But the technology is still complicated,” he says.
The second area where we can expect a breakthrough in the coming years is quantum computers. Several scientific groups from different countries are trying to achieve the so-called quantum superiority, that is, the ability to solve problems that are inaccessible to classical computers.
The media has reported success several times in recent years, but then denied it.
“Quantum supremacy is a moving target. Classic algorithms for simulating quantum systems are also evolving. It’s a kind of race, a dynamic process. At some point, it was considered impossible to simulate Google ’s quantum processor . But competitors did it,” Straupe explains. — Next, the Chinese introduced a quantum processor with a large number of qubits. And so on. But it is clear that sooner or later this superiority will be achieved. Now we are on the verge of it.”
According to Zakharov, we are talking about the next decade. It is expected that quantum superiority will make it possible to make a qualitative leap in the field of material modeling, prediction of the behavior of complex systems, machine learning, and optimization.
Quantum sensing is also developing. “This is an opportunity, due to quantum effects, including quantum entanglement, to measure various parameters with unprecedented accuracy, such as time (which is important for global positioning systems) or electromagnetic fields (for biomedical applications),” says Fedorov.
“Everything is fine with the theory of Russian science”
In 2020 , a roadmap for the development of quantum technologies was approved in Russia . Allocated 51.1 billion rubles. For comparison: in the USA, the Congress approved a project for 20 billion dollars, in Europe there is a Quantum Flagship program with a budget of more than three billion euros, in China they are creating a National Quantum Laboratory with an estimated funding of 12 billion dollars. At the same time, private companies in the West receive huge sums from venture funds for such developments.
As part of the Russian program, it is planned to develop quantum communications, computing, and sensors. We have already created a quantum simulator based on 11 qubits (a qubit is the smallest unit of information in a quantum computer). But for practical application, a quantum computer with thousands of qubits is needed. According to experts, it will be possible to develop such a machine at best by the end of the decade.
“From the point of view of experiments, we also have our victories, but they are still quite modest. The USA, Canada , Japan and China are ahead in this area,” Zakharov admits. keep an eye on what is happening, participate in developments, write our own articles and publish them in international scientific journals.”
According to him, in the field of quantum physics, cooperation with Western colleagues does not stop even in the current difficult situation.
