China already holds the undisputed leadership in quantum supremacy with two computers, one using light and the other superconducting circuits, performing computational feats unattainable for traditional computing.

China has developed two different quantum computers, one that uses light and the other superconducting circuits, and obtained a computing power unattainable for traditional computing, as explained in two articles published in Physical Review Letters.

That means that this dual system of quantum computing gives China the ability to solve practical problems that can not be implemented on conventional computers, stands to respect PhysicsWorld.

With this result, China is already much more than an economic power: together with its energy developments with the artificial sun, it has also entered the "space race" of the 21st century with force, with different projects oriented to Mars and the Moon.

__Pioneers in quantum information__

The new quantum computers have been developed by two groups from the Hefei National Laboratory of Physical Sciences, China University of Science and Technology, led by Professor Jian-Wei Pan, whose work has been highlighted in the past, both by the journal Nature and Science, as a pioneer in experimental quantum information science.

Last July, China announced that it had achieved quantum supremacy with a supercomputer called the Zuchongzhi, capable of performing operations much faster than Google's quantum computer.

Zuchongzhi completed a complex calculation in just over an hour, doing it about 60,000 times faster than a classic computer: Using 56 qubits, he solved in just 1.2 hours a task that would take a classic supercomputer eight years.

__Two new quantum computers__

China now emerges with a new quantum computer, which it calls Zuchongzhi 2.1 , which uses 66 qubits and is 10 million times faster than the current fastest supercomputer: its computational complexity is more than 1 million times greater than the Sycamore processor. of Google.

It also emerges with another quantum supercomputer, which it calls Jiuzhang 2.0 , that uses light to process information, rather than the superconducting circuits that underpin Zuchongzhi 2.1.

"Jiuzhang 2.0", with 113 photons transmitting qubits, is a septillion times more powerful: it can solve in a millisecond an operation that the fastest computer in the world would take 30 billion years.

This second development also represents quite a feat over the previous version of this same quantum computing system based on light, the "Jiuzhang", presented at the end of 2020 and with which 76 qubit transmitting photons were used.

__Quantum supremacy__

With these developments, China consolidates its global quantum advantage and confirms that quantum computers are much more powerful and efficient than classical computers in solving critical problems.

Classical computers are based on the binary system, in which each symbol constitutes a bit, the minimum unit of information in this system, which can only have two values (zero or one).

These classic computers have managed to increase their power through supercomputers, which appeared in the 70s of the last century.

These supercomputers, better known as high-performance computers , base their extraordinary capabilities (measured in petaflops) on the sum of powerful binary computers linked together to increase their working power and performance.

__Another universe__

Quantum computing belongs to another universe: it uses a completely different and superior basic unit of information called the qubit.

The qubit, unlike the bit, can take several values at the same time, that is, it manifests a quantum system with two simultaneous eigen states.

While the bit takes on values of 0 or 1 in groups of 8,16,32 or 64 bits, the measurement in qubits can be in both states of 0 and 1 simultaneously, giving you the ability to perform unreachable operations to binary computing.

Quantum supremacy is achieved when it is shown that a qubit-based computer can solve something that is not available to binary computers, even if they are very sophisticated.

__Double supremacy__

Although it has been claimed in the past that quantum supremacy has already been achieved, and became a battleground between IBM and Google, China has overtaken both with far more powerful developments that, according to Physics magazine, give it no place. to doubt the real and verified quantum supremacy.

And not only that, but it has achieved it by following two different and parallel paths that fortify its supremacy: that of light and that of superconducting circuits.

Physics highlights that it is very difficult for classical algorithms and computers to improve China's quantum advantages, so we can say that the debate on whether quantum supremacy really exists has concluded.

__Useful Supremacy?__

And the magazine concludes: Given that quantum machines solve such large and impressive problems in a way that far surpasses classical simulators, could we use these quantum computers to solve useful computational problems?

Researchers have claimed that these quantum computers can tackle important problems, particularly in the field of quantum chemistry, but no convincing experimental demonstration has yet been reported.

__References__

Strong Quantum Computational Advantage Using a Superconducting Quantum Processor. Yulin Wu et al. Phys. Rev. Lett. 127, 180501. DOI: https: //doi.org/10.1103/PhysRevLett.127.180501

Phase-Programmable Gaussian Boson Sampling Using Stimulated Squeezed Light . Han-Sen Zhong et al. Phys. Rev. Lett. 127, 180502. DOI: https: //doi.org/10.1103/PhysRevLett.127.180502

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