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Quantum Supremacy: How the Quantum Computer Revolution Will Change Everything

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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.” on Friday, May 19th, 2023 at 5:15 am and is filed under Quantum, Rage Against Doofosity, Speaking Truth to Parallelism. Most of the big breakthroughs so far have been in controlled settings, or using problems that we already know the answer to. In any case, reaching quantum supremacy doesn’t mean quantum computers are actually ready to do anything useful.

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. 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.”President Joe Biden inspects a quantum computer at an IBM facility in New York state, October 2022. Photograph: Andrew Harnik/AP Thank you. Physicists are unusually polite group of people. The way you detect someone is not worth listening is the deafening silence around them from their peers. A good advice with cranks, but when money, government or the public is involved, someone should say something. Kaku is just cynically making money. 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.

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.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.

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. 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. 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.

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. When I was a teenager, I enjoyed reading Hyperspace, an early popularization of string theory by the theoretical physicist Michio Kaku. I’m sure I’d have plenty of criticisms if I reread it today, but at the time, I liked it a lot. In the decades since, Kaku has widened his ambit to, well, pretty much everything, regularly churning out popular books with subtitles like “How Science Will Revolutionize the 21st Century” and “How Science Will Shape Human Destiny and Our Daily Lives.” He’s also appeared on countless TV specials, in many cases to argue that UFOs likely contain extraterrestrial visitors. 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.

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