PBS Space Time
4 HN recommenders · recommended in 7 months, 2017–2025
14:40 · 2.9M views · Aug 10, 2016
PBS Space Time explains the quantum eraser experiment, in which erasing which-path information appears to reverse causality in a double-slit setup. It discusses what this means for quantum mechanics.
HN recommends it as a quick introduction to the quantum eraser and delayed choice weirdness, though one commenter notes later corrections to its framing.
8 comments from Hacker News
One of the more head exploding experiments I've seen regarding entanglement is this one: [LINK] By all apparences, it seems to violate causality. It's one of those things that make you suddenly stop and bemusedly wonder if maybe we've finally found a kludge in the Universe's code. edit BTW, if you'd like to know more about this experiment and why it has ridiculous implications, check this PBS clip: this video
If you place a detector in front of (or behind!) the slits the wave function collapses and there is no interference pattern. This is all part of the mystery of it, as soon as you 'observe' a particle, in any way, it stops acting like a wave. See the Delayed Choice Quantum Eraser experiment for even more weirdness, a good video on it: this video
Here's a dumbed down version: [LINK] Also not directly related video if you like your mind being blown: this video Especially given how our understanding of the world changed during the last 200 years, I would say we are still very much clueless. I find that exciting. Btw, no idea why did researchers get "freedom of choice" involved.
Indeed, a quick video from space time for those being first introduced. It’ll likely make you even more confused to the double slit experiment. this video
> Exactly. I don't know why Haskell fanboys insist on abstracting us so far from the machine. I believe it is because abstractions are the way we have always made progress. Is the C code that's so close to the machine not just an abstraction of the underlying assembly, which is an abstraction of the micro operations of your particular processor, which in turn is an abstraction of the gate operations? The abstractions allow us to offload a significant part of mental task. Imagine trying to write an HTML web page in C. Sure it's doable with a lot of effort, but is it as simple as writing it using abstractions such as the DOM? > We live in a mutable physical universe that corresponds to a procedural program. One thing happens after another according to the laws of physics (which are the procedural program for our universe). You just proved why abstractions are useful. "One thing happens after another" is simply our abstraction of what actually happens, as demonstrated by e.g. the quantum eraser experiment [1][2]. [1] [LINK] [2] this video