Another quantum computer reached quantum advantage – does it matter?

A quantum computer may have reached a “quantum advantage” by performing a task which is firmly out of reach of the best supervisors in the world. Experts estimated that the replication of calculation on a classic machine would take billions of billions of times the age of the universe. But what does this feat mean for the development of really practical quantum computers?

The new recording medium is a quantum computer called Jiuzhang 4.0 which makes calculations using light particles or photons. Chao-Yang read at the University of Science and Technology of China and its colleagues used it for the sampling of Gaussian Boson (GBS), a task where a sample of photons is measured after the particles have traveled the sprawl and complex distribution of the computer of mirrors and beam separators.

The previous records for this task involved less than 300 photons, but in this case, Jiuzhang used 3090 particles. It is an improvement ten times, which indicates an increase in the computing power. Read and his colleagues estimated that an advanced algorithm on the most powerful supercomputer in the world would take 10⁴² Years to simulate what Jiuzhang finished in 25.6 microseconds.

“The results are, without a doubt, an impressive technical achievement,” explains Jonathan Lavoie to the Canadian quantum calculation start-up Xanadu, who held a previous GBS record of 219 photons. Chris Langer in quantum Computing Quantinium society, which previously demonstrated the quantum advantage with a different type of quantum computer, says it is a significant advance. “I think it is important that quantum systems can prove that they are not simulable,” he said.

But a jiuzhang machine has already been here. Several times, the researchers have used previous versions of the quantum computer to demonstrate the GBS with a high number of photons that seemed impossible to simulate traditional computers. Each time, they have been thwarted while conventional computers have reproduced their results, sometimes in less than an hour.

Bill Fefferman at the University of Chicago in Illinois, who worked on one of these victorious classic algorithms, says that a crucial concern has hampered the camera: many photons are lost when they move to the quantum computer, and therefore the device is noisy. “Here, they have reduced their noise rates, and at the same time have made the experience greater, which – at least for the moment – seems to lead to the struggle of our algorithm,” explains Fefferman.

Lu says that overcoming the loss of photons was the biggest challenge that his team had to take up in the new experience. But Jiuzhang is still not completely free of noise, which leaves some room for new classic simulation strategies to challenge its status as champion.

“In my opinion, they are not yet in the regime where we can be convinced that no strategy of this type is possible,” explains Jelmer Rema at the University of Twente in the Netherlands.

There is a “virtuous cycle” here, where the competition between classic algorithms and quantum devices brings us closer to the understanding of the elusive border between the classic and quantum worlds, explains Fefferman. In terms of fundamental science, this is a victory for everyone – but if it moves quantum computers to machines that are more powerful in a useful way is a distinct problem.

Langer says that GBS is an “entry -level reference” in the sense that it establishes the difference of a quantum computer compared to conventional computers, but the realization is not reflected directly on the usefulness of the computer. From the point of view of rigorous mathematical theory, it is difficult to assess when the GBS is evidence of “smoking pistol” of the quantum advantage and to identify a clear route to make a machine which excels at GBS in one which excels in a more applied task, explains Nicolás Quesada in Polytechnique Montreal in Canada.

This is partly due to the fact that Jiuzhang’s equipment is highly specialized, so the quantum computer cannot be programmed to perform any calculation. “Although it can demonstrate a calculation advantage for a narrow task, there is a lack of crucial elements for the quantum calculation tolerant with breakdowns and useful,” explains Lavoie. Here, tolerance to breakdowns refers to the calculations where the quantum computer identifies and corrects its own errors, a capacity for a long time which has not yet been carried out in practical quantum computers.

At the same time, Lu and his team presented several requests for Jiuzhang’s exceptional capacity with regard to the GBS. The process can improve relevant calculations for image recognition, chemistry and certain mathematical problems related to automatic learning. Fabio Sciarrino at the University of Sapienza in Rome in Italy says that this approach to quantum computer science is still in its infancy – but in the event of success, it could give birth to a whole new paradigm.

More specifically, the progress of the material – like this last Jiuzhang device – could allow researchers to create quantum computers based on exceptional light, explains Sciarrino. They would be programmed in a completely new way and excel in tasks related to automatic learning.