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Quantum Computer: A Quantum Superiority?

2019-10-23T14:13:09.483Z

Google announces the "Quantum Supremacy": Its Sycamore chip is expected to be dramatically faster than any supercomputer so far. IBM researchers doubt the breakthrough.



Google has developed a computer that can solve problems in minutes, for which previous supercomputers take thousands of years. This has reached the QuantumSupremacy , to German "quantum superiority". This is stated by Google in a blog post and in a study published on Wednesday in the scientific journal Nature ( Nature: Arute et al., 2019).

Thus, the company confirms the reports of the end of September, according to which Google, at least in part, wants to have a functioning quantum computer built. The basis of the system is a quantum processor called Sycamore, on which 54 individually programmable quantum bits (qubits) work. These qubits do not work like traditional bits, which can either take the value 1 or 0. Depending on the quantum mechanical manipulation, qubits can adopt both states simultaneously and remain in this superposition, the superposition, until the end of a calculation. In addition, they can entangle each other.

Thus, two qubits can be in four states simultaneously, and this number grows exponentially. Thus, with the 53 qubits from Sycamore involved in the computation, a representation of 2 ^ 53 states is possible. This means that significantly more computational operations can be performed concurrently than in traditional computers. And correspondingly faster complex tasks can be solved.

How much faster, Google describes in a paper: For the calculations used in the study, the Sycamore processor took only 3:20 minutes. The best supercomputers need estimated at present 10,000 years. The test consisted, very simply expressed, of a calculation for complex random numbers. The researchers took a random series of manipulations of the qubits, repeated the sequence millions of times, and recorded the results. For comparison, the results were calculated using a conventional supercomputer. As Google employee told a video (see above), one had eventually reached the point at which the Supercomputer no longer came.

Criticism of quantum superiority

"It's the 'world world' moment we've been waiting for," writes Google's CEO SundarPichai in a blog post. The discovery ranks among the first missiles launched into space, which paved the way for the exploration of outer space. Quantum computers, Pichai said, could be used in the future to develop better batteries, combat climate change, and research drug discovery, although "it will take many more years to implement a wider range of real world applications."

He has solved no urgent problem or replaced other transport options. William D. Oliver, computer scientist in "Nature"

In the professional world, Googles' alleged quantum superiority meets with mixed reactions. On one side, experts talk about a groundbreaking development. It is certainly a milestone, says Frank Wilhelm-Mauch, professor of quantum theory at the University of Saarland. "The demonstration reminds me of the Wright brothers' first flight," writes MIT computer scientist William D. Oliver in an accompanying text in Nature, "It has not solved an urgent problem or replaced other means of transport." But it had a signal effect and showed what was possible.

On the other hand, there is also criticism, including the experimental setup. It was specially tailored to the strengths of the system, but has virtually no significance. The calculation of a specific problem is currently not possible, because the error rate is still too high and in the presented experiment has been compensated for only by the constant repetitions. The danger of quantum computers cracking common encryption techniques in seconds is therefore theoretically given, but practically some time away.

Researchers at IBM, which is also developing a quantum computer, have just a few days ago expressed doubts about the described superiority of the Google system. In a paper ( arXiv : Pednault et al., 2019) they write that the colleagues did not properly exploit the capacities of the supercomputers. These could solve the problem not only in 10,000 years, but with proper configuration in about 2.5 days - which would then refute the claim of quantum superiority.

Anyway, you should always look at the term skeptically, write the scientists. A headline in the sense of "quantum superiority achieved" is indeed irresistible, but also misleading, as long as there is no precise definition of how one actually measures it.

Source: zeit

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Tech/Game 2019-10-23T14:13:09.483Z

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