Sunday, December 18, 2022

Path Integrals and Entanglement with Kenneth Wharton

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Recorded: 2022/11/08 Released: 2022/12/18

Jim talks with Ken Wharton of San Jose State University about how to apply path integrals to situations to entangled particles. Being an equivalent way to compute amplitudes for different experiments, when applied to various experiments, Bell-type correlations, entanglement swapping, delayed choice experiments, and the triangle network, the mathematics gives the same correlations. But, the interpretation of a path integral - a Lorentz covariant description based on local paths - is very different than that of a traditional wave function - a non-local description of the effects of measurements. This leads to a tension in how to interpret entanglement in the first place.
------------------------------------------- Notes:

1. The article that we discussed in this program:
2. Related papers that I read or Ken referred to in the podcast: 3. Books referred to in the program:
  • Feynman, R. QED: The Strange Theory of Light and Matter. [Amazon] A great, non-technical introduction to quantum electrodynamics, and therefore path integrals. As an undergraduate I found it an inspiring text, and when I ran a book club at Xavier for the physics students, we always had a good time when it came around.
  • Griffiths, R., Consistent Quantum Theory. [Amazon]. I have to confess that, although I bought a copy of this book after Randy and I did the episode on Consistent Histories, I have yet to read it.
  • Mattuck, R., A Guide to Feynman Diagrams in the Many-Body Problem. [Amazon] This has the pinball-game description the sum-over-histories approach - before getting into the deepest, darkest forest of constructing Green's functions for probability amplitudes. Since it's a Dover book, the first couple of chapters alone are worth the price. Like I said, the transition from the pinball game to the quantum pinball game was a little too much for me as an undergraduate, but after the recording podcast I've been working through it, and it's really not so difficult -- as long as you're up on your basic non-relativistic quantum mechanics. The reason why the it was called "Feynman Diagrams for Idiots" by graduate students and, looking at the preface to the second addition, much worse by reviewers (especially Russian reviewers) is that it has lots of cartoons scattered throughout the book. These are actually jewels, and are a third reason to pick up this book, either at the physics library or the bookstore, not a reason to avoid it.
  • Aharanov, A. and D. Rohrlich, Quantum Paradoxes: Quantum Theory for the Perplexed. [Amazon] Randy and I started our first podcast with this book. Partially because of that, I've read it three times, cover-to-cover. The Perimeter Institute gave a conference on the topic in 2016, "Concepts and Paradoxes in a Quantum Universe," which you can view either all contributions or just Aharonov's. I have all the talks on mp3 to play in the car (back when PIRSA allowed you to download the mp3's directly - I'm not bitter about the change [Yes I am]).
4. Related Episodes of Physics Frontiers:
5. If you'd like to know more about Ken Wharton, I have some additional questions not about path integrals on YouTube. 5. Please visit and comment on our subreddit, YouTube Channel, or Twitter account. These are also places to look for announcements of new episodes and the like. And if you could help us keep this going by contributing to our Patreon, we'd be grateful.
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