Questions about measurement devices in the double slit experiment

[UnderstandingQT]

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?

 

[PeroK]

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?

What might "detect without recording" mean?

 

[DrChinese]

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?

 

[EPR]

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.

 

[omie]

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?

 

[PeroK]

When they launch the particle, where do they aim specifically?

At the slits! Where else?

 

[Nugatory]

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.

 

[Cato]

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.

 

[Nugatory]

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?"

 

[Cato]

Thank you! So all the talk about the importance of "observation" is mistaken. Nice to have that that settled.

 

[EPR]

If someone were able to explain single/definite outcomes(why certain outcomes and not others), he'd surely have gotten a Nobel prize.