Let N represent the number we wish to factorize. For an ordinary digital computer, the amount of time it takes to factorize a number grows exponentially, like t ~ e N, times some unimportant factors. Because Teller (in Livermore) was able to bring in funding, Livermore’s director refused to rein him in and even prevented other scientists writing corrective letters. Competing labs–Argonne and Los Alamos–had to conduct their own tests to show that proposals don’t work and Teller just came up even more insane plans. In any case, for Kaku, knowledge is power. It’s part of the reason he’s moved from the lab to TV, radio and books. “The whole purpose of writing books for the public is so that [they] can make educated, reasonable, wise decisions about the future of technology. Once technology becomes so complicated that the average person cannot grasp it, then there’s big trouble, because then people with no moral compass will be in charge of the direction of that technology.”

And then there’s the Misconception of Misconceptions, about how a QC “analyzes all possible paths at the same time”—with no recognition anywhere of the central difficulty, the thing that makes a QC enormously weaker than an exponentially parallel classical computer, but is also the new and interesting part, namely that you only get to see a single, random outcome when you measure, with its probability given by the Born rule. That’s the error so common that I warn against it right below the title of my blog. There are other reasons, as well. From an early age, Kaku was, unsurprisingly, a science fiction nut. But he wasn’t content to simply swallow the stories, and wanted to know if they were really possible, whether the laws of physics might verify or contradict them. “And in the science section, there was nothing, absolutely nothing. And I was [also] fascinated by Einstein’s dream of a theory of everything, a unified field theory. Again I found nothing, not a single book, on Einstein’s great dream. And I said to myself, when I grow up, and I become a theoretical physicist, I want to write papers on this subject. But I also want to write for myself as a child, going to the library and being so frustrated that there was nothing for me to read. And that’s what I do.” This is a double howler: first, trial division takes only ~√N time; Kaku has confused N itself with its number of digits, ~log 2N. Second, he seems unaware that much better classical factoring algorithms, like the Number Field Sieve, have been known for decades, even though those algorithms play a central role in codebreaking and in any discussion of where the quantum/classical crossover might happen. President Joe Biden inspects a quantum computer at an IBM facility in New York state, October 2022. Photograph: Andrew Harnik/AP Have you been feeling anxious about technology lately? If so, you’re in good company. The United Nations has urged all governments to implement a set of rules designed to rein in artificial intelligence. An open letter, signed by such luminaries as Yuval Noah Harari and Elon Musk, called for research into the most advanced AI to be paused and measures taken to ensure it remains “safe … trustworthy, and loyal”. These pangs followed the launch last year of ChatGPT, a chatbot that can write you an essay on Milton as easily as it can generate a recipe for everything you happen to have in your cupboard that evening.

Quantum computers aren’t just about doing things faster or more efficiently. They’ll let us do things that we couldn’t even have dreamed of without them. Things that even the best supercomputer just isn’t capable of.

Google revealed that their Sycamore quantum computer could solve a mathematical problem in 200 seconds that would take 10,000 years on the world’s fastest supercomputer. I am just reading a book about Ronald Reagan’s “Star Wars” Strategic Defense Initiative program. It is horrifying how far Edward Teller was able to convince the President, Congress, Pentagon and the public into his hare-brained visions ( “Brilliant Pebbles”, “Excalibur”, and so on). Pure monomaniacal intensity can bring in billions. Quantum computing could change the world. It could transform medicine, break encryption and revolutionise communications and artificial intelligence. Companies like IBM, Microsoft and Google are racing to build reliable quantum computers. China has invested billions. Quantum simulation speeding up progress in biochemistry, high-temperature superconductivity, and the like is at least plausible—though very far from guaranteed, since one has to beat the cleverest classical approaches that can be designed for the same problems (a point that Kaku nowhere grapples with).Maybe he should have let ChatGPT write it? Something entirely different, could you comment on this paper, pretty please Researchers have made great progress in developing the algorithms that quantum computers will use. But the devices themselves still need a lot more work.