Quote:
Originally Posted by Howard Beale
It's called the 'quantum eraser' bec a detector is placed BEHIND one of the slits and, it was thought, that should disallow a particle from 'knowing' that there's a detector and therefor we'd see the interference pattern but it turns out to not work that way. When we gain ANY which-path information the interference pattern disappears (hence 'eraser'). For some this means that there's an observer problem in QM while others offer up some explanation that says there isn't.
Off to youtube you go w/ 'observer problem QM' bec I don't feel like searching one out.
Quote:
Originally Posted by Howard Beale
It's a wonder that anyone can understand that stuff esp if we have no free will. Anyway, I meant the delayed choice eraser experiment and I stand by what I meant to say.
https://en.m.wikipedia.org/wiki/Dela...quantum_eraser
From the link. Quantum Eraser Section:
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They proposed a "quantum eraser" to obtain which-path information without scattering the particles or otherwise introducing uncontrolled phase factors to them. Rather than attempting to observe which photon was entering each slit (thus disturbing them), they proposed to "mark" them with information that, in principle at least, would allow the photons to be distinguished after passing through the slits. Lest there be any misunderstanding, the interference pattern does disappear when the photons are so marked.
However, the interference pattern reappears if the which-path information is further manipulated after the marked photons have passed through the double slits to obscure the which-path markings. Since 1982, multiple experiments have demonstrated the validity of the so-called quantum "eraser".
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What's in bold is why it's called "Eraser". If the which-path information is later obscured (Erased) the interference pattern reappears. However, it should be noted this erasure takes place for a subset of particles which can be picked out from the totality of particles landing on the "screen" to show the interference pattern for the subset.
However, there's a problem with this experimentally.
From the link:
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Elementary precursors to current quantum-eraser experiments such as the "simple quantum eraser" described above have straightforward classical-wave explanations. Indeed, it could be argued that there is nothing particularly quantum about this experiment.
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Nevertheless, Jordan has argued on the basis of the correspondence principle, that despite the existence of classical explanations, first-order interference experiments such as the above can be interpreted as true quantum erasers.
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So they went to the Delayed Choice Quantum Eraser. They split the photons into entangled pairs called the "Signal" and "Idler". They look at distribution patterns of the Signal photons and of subsets of the Signal Photons where subsets of the Signal Photons are identified by the delayed arrival of entangled Idler pairs. Subsets of the Entangled Idler pairs are identified by grouping them into categories where which-way information is identified and where it has been "Erased". From the perspective of the Entangled Signal Photons the "Erasure" on corresponding Idler Photons is "Delayed". i.e. it takes place AFTER the Signal photon has landed on the "Screen".
The which-way marking of the Idler Photon takes place while its entangled Signal Photon is still in flight. So the Signal Photon "knows" the marking at that time by entanglement. The Signal Photon then lands on the screen. After that, its entangled Idler Photon is randomly mixed with other marked Idler Photons so as to "Erase" their which-way information. The Idler Photon then lands on the detector and by its timing identifies its entangled Signal pair that's already landed. The subset of Signal Photons thus identified shows an interference pattern.
By this Delay of the erasure of which-way information until after the signal photon lands on the screen there is no longer the problem of a possible classical explanation.
See "The experiment of Kim et al. (1999)" from the link.
PairTheBoard
Last edited by PairTheBoard; 09-06-2019 at 01:39 AM.