Quantum mechanics

Physics World

I bumped into the Physics World website again the other day. As you are doubtless aware, it’s a digital and printed magazine produced by the UK Institute of Physics. The latter is also known as the IOP. It’s the “professional body and learned society for physics in the UK and Ireland”. There’s various articles giving news about physics: Screenshot of Physics World 30th April 2024 The picture of the circuit board refers to an article by Tim Wogan called Bolometer measures state of superconducting qubit. A…

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Quantum entanglement history II

As I was saying last time, the 2022 physics Nobel Prize was awarded to John Clauser, Alain Aspect, and Anton Zeilinger for their contribution to quantum entanglement. This is associated with instantaneous “spooky action at a distance”, and is said to play an important role in quantum computing. It all started in 1935 with the EPR paper, where Einstein, Podolsky, and Rosen said quantum mechanics must be incomplete because it predicts a system in two different states at the same time. Bohr gave a rambling off-topic…

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Quantum entanglement history I

The 2022 Nobel prize in physics was awarded to Alain Aspect, John Clauser and Anton Zeilinger "for experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science". Hamish Johnston gave a brief account in Physics World on October 4th. He said the three laureates performed the key experiments that established the quantum property of entanglement. That’s quantum entanglement, which is often described as spooky action at a distance. The idea is that you produce two photons from one event, and when…

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Even physicists don’t understand quantum mechanics

Check out Sean Carroll’s New York Times article Even Physicists Don’t Understand Quantum Mechanics. I thought it was great. And I just loved that subtitle: Worse, they don’t seem to want to understand it. Carroll started by quoting Feynman, who said this: “I think I can safely say that nobody really understands quantum mechanics”. That’s a good start. Feynman was known as the great explainer, but he couldn’t explain how a magnet works. Or how gravity works. Moreover he was a major contributor to quantum electrodynamics,…

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Quantum physics is cargo cult science

Ethan Siegel wrote a blog post this week called This Is Why Quantum Field Theory Is More Fundamental Than Quantum Mechanics. I read it and sighed, because so much of it is misleading. This sort of thing has been in the air recently, because Lee Smolin gave a lecture on Einstein's unfinished revolution. Smolin said quantum mechanics was incomplete, then doubled down and said it was wrong. I think he's right, only more than he knows. So I thought I'd use Siegel's post to show just…

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Einstein’s unfinished revolution

Lee Smolin gave a lecture at the Perimeter Institute this week. Here’s the blurb: “On April 17, in a special webcast talk based on his latest book, Einstein’s Unfinished Revolution, Perimeter’s Lee Smolin will argue that the problems that have bedeviled quantum physics since its inception are unsolved and unsolvable for the simple reason that the theory is incomplete. There is more to quantum physics waiting to be discovered”. This sounds interesting. It's definitely my kind of thing. Let’s take a look. 00:49 Greg Dick starts…

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Quantum computing and the quantum quacks

I have a computer science degree. I work in IT, and have done so for many years. In that period "classical" computers have advanced by leaps and bounds. I remember teletypes and paper tape, and punched cards too. I also remember when a top-notch disk drive was the size of a washing machine and the cost of a car. It provided a miserly 10 megabytes of storage. My disk drive today is the size of my wallet and cost £46.99. It provides a terabyte of storage.…

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A potted history of quantum mechanics

There’s some ambiguity when it comes to quantum mechanics. Some people apply the term widely, others apply it to the theory that was developed in the 1920s to replace the old quantum theory. There’s some ambiguity with that too, in that the old quantum theory was primarily an atomic model proposed by Niels Bohr in 1913 and extended by Arnold Sommerfeld in 1916. It didn’t include the quantum nature of light, which arguably began with Max Planck’s black-body paper in 1900. Or with Albert Einstein’s photoelectric…

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The old quantum theory and Bohr

In 1911 Niels Bohr was in Cambridge. He had a Carlsberg fellowship grant and a postdoc position at the Cavendish lab under JJ Thomson. However there were issues, and he ended up transferring to Manchester and Ernie Rutherford. You can read about it in JJ Thomson and the Bohr atom by John Heilbron dating from 1977. Heilbron says “far from being merely ‘scientific curiosities’ JJ Thomson's seemingly naive models actually contained some of the fundamental ideas of Niels Bohr's revolutionary quantum theory of the atom”. He…

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The old quantum theory begins

Quantum physics or quantum theory can arguably be traced back to Gustav Kirchhoff's researches on the solar spectrum. See his 1860 paper on the relation between the radiating and absorbing powers of different bodies for light and heat. Kirchhoff spoke about black body radiation and what came to be known as the black body problem. When a body is heated such that it emits light, the colour of its glow depends on its temperature alone. As you heat a poker in a fire it glows cherry…

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