Questions about measurement devices in the double slit experiment

Click For Summary

Discussion Overview

The discussion revolves around the measurement devices used in the double slit experiment, particularly focusing on whether these devices must record measurements to cause wave function collapse, and the implications of detection without recording. Participants explore concepts related to quantum mechanics, measurement, and the nature of observation in experiments.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Exploratory

Main Points Raised

  • Some participants question whether devices that quantify which slit light passes through must record measurements to induce wave function collapse, suggesting that mere detection may not suffice.
  • It is proposed that placing polarizers over the slits can prevent interference without recording which slit the light goes through, raising questions about the nature of measurement and observation.
  • Participants discuss the implications of turning detectors on or off, with one suggesting that if detectors are on but not observed, it remains unclear whether an interference pattern would emerge.
  • Another participant asserts that the interaction with detectors is what prevents the interference pattern, claiming this has been definitively settled in the past.
  • There is a reference to a common misconception regarding the role of conscious observers in the measurement process, indicating a debate about the interpretation of quantum mechanics.

Areas of Agreement / Disagreement

Participants express differing views on the necessity of recording measurements for wave function collapse, with some asserting that detection alone is sufficient while others challenge this notion. The discussion remains unresolved regarding the specifics of how observation affects the interference pattern.

Contextual Notes

There are limitations in the discussion regarding the definitions of "detection" and "recording," as well as the assumptions about the nature of measurement in quantum mechanics. The implications of these definitions on the outcomes of the experiment are not fully explored.

UnderstandingQT
Messages
1
Reaction score
0
How did you find PF?: Google

Is it true that the devices that quantify which slit do NOT produce wave collapse unless they actually record the light measurements rather than just detect them without recording?
 
Physics news on Phys.org
UnderstandingQT said:
How did you find PF?: Google

Is it true that the devices that quantify which slit do NOT produce wave collapse unless they actually record the light measurements rather than just detect them without recording?
:welcome:

What might "detect without recording" mean?
 
  • Like
Likes   Reactions: Omega0
UnderstandingQT said:
Is it true that the devices that quantify which slit do NOT produce wave collapse unless they actually record the light measurements rather than just detect them without recording?

It is possible to place polarizers over each of the 2 slits. In cases where the slits are aligned perpendicular, there will be no interference. And yet there is nothing being recorded in any fashion to indicate which slit the light goes through, even though in principle that is possible.

http://sciencedemonstrations.fas.ha...-demonstrations/files/single_photon_paper.pdf

Is that the scenario you are envisioning?
 
  • Like
Likes   Reactions: vanhees71
UnderstandingQT said:
How did you find PF?: Google

Is it true that the devices that quantify which slit do NOT produce wave collapse unless they actually record the light measurements rather than just detect them without recording?
You can record which slit they went through and in that case there would be no interference pattern.
 
DrChinese said:
It is possible to place polarizers over each of the 2 slits. In cases where the slits are aligned perpendicular, there will be no interference. And yet there is nothing being recorded in any fashion to indicate which slit the light goes through, even though in principle that is possible.

http://sciencedemonstrations.fas.ha...-demonstrations/files/single_photon_paper.pdf

Is that the scenario you are envisioning?
When they launch the particle, where do they aim specifically?
 
omie said:
When they launch the particle, where do they aim specifically?

At the slits! Where else?
 
omie said:
When they launch the particle, where do they aim specifically?
The slits are close enough together that they're both equally likely to be hit. It's possible to do the experiment with the slits more widely separated (which has the effect of weakening the interference pattern and making it asymmetrical) but that just complicates the calculation without introducing any new physics.
 
  • Like
Likes   Reactions: omie
I have a similar and (maybe the same?) question as UnderstandingQT. If you fire electrons toward the two slits, and you have electron detectors at each slit that are turned off, then you will get an interference pattern. If you turn the detectors on and observe the results, you will not get an interference pattern. If you turn the detectors on but do not observe or record the results, will you get an interference pattern? The question, of course is trying to sort out whether the interference pattern vanishes because 1) a conscious observer was aware of which slit the electron passed through or 2) whether the mere physical process that permitted detection of the electron caused the electron to behave as a particle. Surely this obvious high-school level question has been definitively settled.

Sorry, Understanding QT, if this is not what you were getting at.
 
Cato said:
If you turn the detectors on but do not observe or record the results, will you get an interference pattern?
No. It's the interaction with the detectors that makes the difference.

This was definitively settled many decades ago. Unfortunately by then the idea that a conscious observer was involved had made it into the popular imagination where it lives on as a sort of urban legend, one of those things that everyone has "just heard somewhere"

A pretty good layman friendly reference is David Lindley's book "Where did the weirdness go?"
 
Last edited:
  • #10
Thank you! So all the talk about the importance of "observation" is mistaken. Nice to have that that settled.
 
  • #11
If someone were able to explain single/definite outcomes(why certain outcomes and not others), he'd surely have gotten a Nobel prize.
 

Similar threads

Undergrad Which-Path from Global Momentum Measurement in Double Slit
  • · Replies 3 ·
Replies
3
Views
700
Undergrad Single vs. Double slit coherence clarification please
  • · Replies 10 ·
Replies
10
Views
2K
High School Double-slit experiment and time
  • · Replies 24 ·
Replies
24
Views
3K
Undergrad Is There A Study Showing The Observer Effect Ignoring Conscious Intent?
  • · Replies 3 ·
Replies
3
Views
5K
High School Yet another double slit thought experiment...
  • · Replies 20 ·
Replies
20
Views
2K
Undergrad "Wave-particle duality" and double-slit experiment
  • · Replies 36 ·
2
Replies
36
Views
8K
High School How is the measurement done for the double slit experiment?
  • · Replies 3 ·
Replies
3
Views
2K
High School What is causing destructive interference in double slit experiment?
  • · Replies 32 ·
2
Replies
32
Views
4K
High School Double Double Slit Experiment -- Question about Variations
  • · Replies 3 ·
Replies
3
Views
2K
High School Q - Double slit experiment, delayed slit selection observation
  • · Replies 5 ·
Replies
5
Views
2K