# Tag Info

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I'm assuming your input photon has a known polarization (say horizontal). You won't see interference, because the polarizers act as a "which-path" measuring device. If you erase the polarization information, the interference pattern will appear.

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You can model the wave function as collapsing into either $|slit1\rangle$ or $slit2\rangle$ when the electron passes through the slits, or when the electron hits the detector, or when a human experimenter comes along and examines the results. The corresponding theories make all the same predictions (this is a theorem of von Neumann), so it's entirely up to ...

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Let's imagine the double slit experiment you proposed as something simpler, yet equivalent. In the electron beam experiment you have a free particle's wavefunction that suddenly faces a decision: go left or right, and then collapses at a screen, giving you a result. I propose finding an analogous example with spin: suppose we have a hydrogen atom trapped ...

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This experiment has been done, first by Birgit Dopfer in 1998, then later by Dr. John Cramer of the University Of WA. In Dopfer's experiment, there was a "coincidence detector" which is basically an AND gate to filter out only the entangled pairs. By moving the detector in the beam of photons not going to the double-slit, the information about the photon's ...

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The answer by Craig Gidney is quite adequate for the question, but I want to address the word "collapse" in the title, since search engines will be homing in on it. From webster.com 1: to fall or shrink together abruptly and completely : fall into a jumbled or flattened mass through the force of external pressure <a blood vessel that collapsed> ...

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Note that your first video is showing a simulation of the experiment. From the transcript: We don't have the equipment to do it for you, but we can show you a simulation of what you would see. Right now, you are watching an animation showing what we would expect to see if we could do the double slit experiment with only a small number of photons in a ...

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Suppose the amplitude of the wave from slit $1$ arriving at a point is $A_1$ and the amplitude of the wave from slit $2$ arriving at the same point is $A_2$ and let $A_2>A_1$. The relative phase between the waves from the two slits arriving at that point depends on the path difference between the slits and the point and not on the amplitude of the waves. ...

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The bright fringes will get darker as the intensity of the bright fringes is when the two beams interact constructively and the intensity becomes proportional to the sum of the two beam intensities. In the destructive interference case the light beam intensity becomes proportional to the difference of the two beam intensities which if equal will lead to ...

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The diagrams that typically figure in textbooks and pop-sci books have the transverse scale massively exaggerated. The slits for a optical wavelength version of the experiment are typically less than a millimeter apart and on order of a tenth of a millimeter or less in width. This means that they are separated by less than the natural width of the incident ...

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The part of the data collection and its consequences to the result of the experiment, as presented in the video you provided, seems to be wrong. At least it never happened the way, the speaker wants to make us believe. Chapter from the Wikipedia Article about the Double-slit experiment: "Which-way" experiments and the principle of complementarity ...

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Measurements disturb the double slit experiment because of the particle nature of light and matter. In order to measure which slit the electron passes through there must be some sort of interaction to detect the electron. By putting a capacitor in the way, you would drastically affect the particle. Think of it like putting a hose-pipe in front of a ...

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I wrote my Master Thesis on partially coherent classical wave fields applied to gratings, so I will try to give some insight on what exactly about the double slit makes it a quantum problem and what is really just classical wave mechanics. This should simplify the discussion a bit by separating the two issues (at least hopefully). General comment on the ...

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It's unnecessary to check it for particular functional forms. After all, the functional forms aren't exact. In particular, it's not true that the intensity at all interference minima is strictly zero. The minima away from the center of the picture are closer to one of the slits, so the wave function from the slit is larger (in absolute value), and therefore ...

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It does not depend on an observer or being observed at all. Interference requires things to be arranged in a perfect way. If you introduce anything into the experiment in an attempt to observe you will disturb the pattern. If you shine light on the experiment you mess it up. If you place devices somewhere in the experiment you will mess up the pattern by ...

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To me, an 'observer' in this sense means something that can take a 'measurement' of the photon (or electron) as it travels through the slits (like an observation instrument), and thus altering its wave-function. If the observer can't take measurements, then he can't alter the events, and the same thing will happen whether or not he is there.

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