Sep 25, 2019 23:00:00

What does “quantum transcendence” that Google has demonstrated and quantum computers have made great progress mean?

by

geralt

Many media reported on September 20, 2019 that NASA has inadvertently published a paper by a Google researcher on its website, saying that Google has demonstrated quantum transcendence. Although the paper has already been deleted, computer scientist Scott Aaronson has answered the FAQ 'What is quantum transcendence?'

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https://www.scottaaronson.com/blog/?p=4317

◆ What is quantum transcendence?
Quantum transcendence is a term that indicates that a quantum computer has computing power that cannot be achieved with a conventional computer. It should be noted when using the term quantum transcendence that the problem is solved 'quantitatively' and 'reliably' first. And it is a problem that is difficult to solve by the conventional method. And that speed up can be expected in the near future. It is important that problem solving helps people, but this is not essential.

If Google realizes quantum transcendence, will there be no unreadable code?

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Some say that with the realization of quantum computers, it will be possible to decode codes that cannot be decoded in 2019. However, devices developed by IBM and Google are 50 to 100 qubits and do not perform error correction. It is said that thousands of qubits are required to run the Shore algorithm and break the RSA cipher , and it is still not possible to achieve with existing Google technology. It is expected that a higher level of technology will be born if error correction methods are used, but it will take time to realize.

And Aaronson believes that even if a quantum computer that corrects errors is realized, not all codes can be deciphered. Even if the public key can be broken by the quantum computer, the encryption of the private key is not affected much. In addition, Mr. Aaronson said that “how public keys are broken quantumally” is not fully understood even after more than 20 years of research.

◆ Even if a quantum computer realizes that a conventional computer was difficult, isn't it meaningless if the problem itself has no meaning?
Quantum computers do not solve everything, but they are not meaningless and are 'something that solves some problems'.

Over the past few decades, quantum computers have been said to be 'using billions and spending decades to solve even problems that can be solved with a laptop', but in recent years it has no longer been such a ridicule It is not a target. With conventional computers, problems that require a large amount of resources can be solved with few resources.

When the Wright brothers invented the Light Flyer , people who thought that “the air travel is fundamentally impossible” initially disregarded the “swift vehicle with a propeller”. There are comments all over the Internet that neglect quantum computers, but Aaronson said quantum computers are the same as the Light Flyer.

◆ Experiments conducted by quantum computers are checked by conventional computers. This means that traditional computers can simulate the same experiments as quantum computers, even at slow speeds. Can it still be called “quantum transcendence”?
In response to this question, Aaronson said, “Using a 53 qubit chip can achieve millions of times faster. As the number of qubits increases, this rate increases exponentially. Predicted by the analysis, there is no limit here. '

Is there a use for sampling-based quantum computers?

by MichaelWuensch

So far, the answer to this question has been considered “no”, but the situation is changing. In recent years, it is thought that it can be applied to cryptocurrency protocols and blockchain network mechanisms ' proof of stake ', and it is possible that other application fields may be found in the future.

Quantum mechanics can break the upper limit of Bell's inequality , but isn't this a quantum transcendence?
This confuses the way the language is understood, and it is another form of “quantum transcendence” regarding Bell's inequality. `` Quantum supremacy '' in the sense of breaking Bell's inequality can be said to be `` quantum correlational supremacy '', and in recent years `` quantum computational supremacy ( It is different from “computational transcendence of quantum”.

Have you invented the concept of quantum transcendence?
“No” to this question, Aaronson said. Mr. Aaronson played a part in the formation of the concept of quantum transcendence. The term quantum transcendence was created in 2012 by theoretical physicist John Preskill, but the core of the concept dates back to the quantum computing itself that has existed since the 1980s.

In 1994, factoring large numbers using Shore's algorithm was one of the main experiments showing quantum transcendence. The idea of demonstrating quantum transcendence using the sampling problem has been proposed since around 2002, and one of them, the method of “random circuit sampling”, was sent by Mr. Aaronson in December 2015. It was born from email. After that, Google did a lot of random circuit sampling analysis and deepened research on quantum computing.

What does it mean for skeptics of quantum computers when quantum transcendence is achieved?
“I don't want to be them now,” said Aaronson. “They were able to change their minds that 'quantum transcendence is possible', such as my good friend Gil Karai, who thought that 'quantum transcendence cannot be achieved for fundamental reasons.' Some have changed their minds, but some still do not change their minds. I don't want to give them an escape. '

What do you think will happen next?

by Lennart Wittstock

One of the next milestones is believed to be the use of programmable 50-100 qubit quantum computers and faster and more useful quantum simulations than traditional computers. Aaronson also said that achieving quantum transcendence and useful error correction in a single system is a milestone.