Well, that’s the universal law of technology, that [it] can be used for good or evil. When humans discovered the bow and arrow, we could use that to bring down game and feed people in our tribe. But of course, the bow and arrow can also be used against our enemies.” Knox #1: As a test, I tried asking GPT-4 to write a quantum computing explainer in the style of Michio Kaku, and it indeed generated similar prose with similar misconceptions. But then I asked it to write it in the style of Scott Aaronson and it did the same… 😀 President Joe Biden inspects a quantum computer at an IBM facility in New York state, October 2022. Photograph: Andrew Harnik/AP

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.” I have found Michio Kaki’s writing to be full of misconceptions for years. He does not represent science well. Maybe he thinks that he is popularising the wonder of science, but he gets so much basic stuff wrong. He is more of a media personality than a scientist I think. Kaku brushes this off. He points to the billions of dollars being poured into quantum research – “the Gold Rush is on” he says – and the way intelligence agencies have been warning about the need to get quantum-ready. That’s hardly proof positive they’ll live up to expectations – it could be tulip mania rather than a gold rush. He shrugs: “Life’s a gamble.” Silicon Valley could become a rust belt … a junkyard of chips that no one uses any more because they’re too primitive You’ll probably never have a quantum chip in your laptop or smartphone. There’s not going to be an iPhone Q. Quantum computers have been theorised about for decades, but the reason it’s taken so long for them to arrive is that they’re incredibly sensitive to interference. The runaway success of the microchip processor may be nearing its end, with profound implications for our economy, society and way of life, even leaving Silicon Valley as a new Rust Belt, its technology obsolete. Step forward the quantum computer, which harnesses the power and complexity of the atomic realm, and may be useful in solving humanity's greatest challenges from climate change, to global starvation, to incurable diseases. Humanity's next great technological achievement already promises to be every bit as revolutionary as the transistor and microchip once were. Its unprecedented gains in computing power and unique ability to simulate the physical universe herald advances that could change every aspect of our lives.They’re powerful, but not reliable. That means that for now, claims of quantum supremacy have to be taken with a pinch of salt. In October 2019, Google published a paper suggesting it had achieved quantum supremacy – the point at which a quantum computer can outperform a classical computer. But its rivals disputed the claim – IBM said Google had not tapped into the full power of modern supercomputers. 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. 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.

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. In any case, he’s far from the only true believer. Corporations such as IBM, Google, Microsoft and Intel are investing heavily in the technology, as is the Chinese government, which has developed a 113 qubit computer called Jiuzhang. So, assuming for a moment quantum dreams do become a reality: is it responsible to accentuate the positive, as Kaku does? What about the possibility of these immense capabilities being used for ill? Honestly, though, the errors aren’t the worst of it. The majority of the book is not even worth hunting for errors in, because fundamentally, it’s filler.How? The main thing to understand is that quantum computers can make calculations much, much faster than digital ones. They do this using qubits, the quantum equivalent of bits – the zeros and ones that convey information in a conventional computer. Whereas bits are stored as electrical charges in transistors etched on to silicon chips, qubits are represented by properties of particles, for example, the angular momentum of an electron. Qubits’ superior firepower comes about because the laws of classical physics do not apply in the strange subatomic world, allowing them to take any value between zero and one, and enabling a mysterious process called quantum entanglement, which Einstein famously called spukhafte Fernwirkung or “spooky action at a distance”. Kaku makes valiant efforts to explain these mechanisms in his book, but it’s essentially impossible for a layperson to fully grasp. As the science communicator Sabine Hossenfelder puts it in one of her wildly popular YouTube videos on the subject: “When we write about quantum mechanics, we’re faced with the task of converting mathematical expressions into language. And regardless of which language we use, English, German, Chinese or whatever, our language didn’t evolve to describe quantum behaviour.”

At this stage, it’s worth introducing an important caveat. Quantum computers are very, very hard to make. Because they rely on tiny particles that are extremely sensitive to any kind of disturbance, most can only run at temperatures close to absolute zero, where everything slows down and there’s minimal environmental “noise”. That is, as you would expect, quite difficult to arrange. So far, the most advanced quantum computer in the world, IBM’s Osprey, has 433 qubits. This might not sound like much, but as the company points out “the number of classical bits that would be necessary to represent a state on the Osprey processor far exceeds the total number of atoms in the known universe”. What they don’t say is that it only works for about 70 to 80 millionths of a second before being overwhelmed by noise. Not only that, but the calculations it can make have very limited applications. As Kaku himself notes: “A workable quantum computer that can solve real-world problems is still many years in the future.” Some physicists, such as Mikhail Dyakonov at the University of Montpellier, believe the technical challenges mean the chances of a quantum computer “that could compete with your laptop” ever being built are pretty much zero. 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.Scott Aaronson has read the book and confirms that it’s every bit as awful as it seems. For a different look at out-of-control quantum […] His book about QFT isn’t half bad, it doesn’t add anything to the Weinberg or Zee but has a very interesting historical foray into simmetries and all the work in the post war era, citing the japanese effort that i knew nothing about. OK, so here Kaku has already perpetuated two of the most basic, forehead-banging errors about what quantum computers can do. In truth, anything that a QC can calculate, a classical computer can calculate as well, given exponentially more time: for example, by representing the entire wavefunction, all 2 n amplitudes, to whatever accuracy is needed. That’s why it was understood from the very beginning that quantum computers can’t change what’s computable, but only how efficiently things can be computed. Quantum mechanics is the foundation of physics, which underlies chemistry, which is the foundation of biology. So for scientists to accurately simulate any of those things, they need a better way of making calculations that can handle uncertainty. Enter, quantum computers. How do quantum computers work? The stuff involving optimization, machine learning, and the like is almost entirely wishful thinking.

Not once in the book has Kaku even mentioned the intellectual tools (e.g., looking at actual quantum algorithms like Grover’s algorithm or phase estimation, and their performance on various tasks) that would be needed to distinguish 1 from 2. 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.Some things are better left unsaid. I ask you, Professor Aaronson – no more posts like these, for the sake of the people and our industry. An exhilarating guide to the astonishing future of quantum computing, from the international bestselling physicist That could mean more efficient products – from new materials for batteries in electric cars, through to better and cheaper drugs, or vastly improved solar panels. Scientists hope that quantum simulations could even help find a cure for Alzheimer’s.