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- Summary
- Thinking on a Young-Wheeler experiment, weak measurements, strong measurements, a 2011 paper, and alice and bob

Hello,

I am interested in weak measures since I discovered this paper:

I understood that retro-causality is only an interpretation and that's not more exploitable than the famous experiments of quantum gum delayed choice.

In fact, we don't control the result of the measurement, the correlations have always been made afterwards, and therefore, there is no communication as in the classical sense .

(We never control the measure, of course, but I continue my development)

Then, there is this famous Wheeler thought experiment like here :

https://en.wikipedia.org/wiki/Wheeler's_delayed-choice_experiment

So I asked myself the question :

What would happen if we repeated Wheeler's famous thought experiment, (Gedankenexperiment as Einstein said) and that we decided to make the appropriate weak measures in F1 and F2, so as not to cause the collapse of the wave function ?

What would we get as results / correlations ?

I continued to search and I found this paper:

I know there have been several debates in PF from that experience as here :

However, I didn't find the answer to my question that really more complex, so I decided to open a new discussion.

Indeed, I read the paper whose link was in the discussion :

I understood correctly :

Ok

But my problem is this:

We all know that the probabilities of impact in a point if we observe in F1 or F2 are different from the probabilities of impact at the same point if we observe the screen :

P1 + P2 = |a1|² + |a2|²

is different from

P12 = |a1 +a2|²

(a = amplitude of probability)

How to reconcile the no-go theorem with the strange possibility that BOB, which make a series of strong measurements (a screen = 1 or no screen = 0, throughout the series), can communicate with ALICE, which systematically make a series of weak measurements (slits), schematically of course, by using the protocol of the experiment described on the paper ?

(we can have a set of several ensemble of equally prepared systems simultaneously on the same table).

I admit that my question is difficult to ask and I often have trouble doing myself understood, so in advance, excuse me for this long post, (and my english !) but this problem don't let me sleep !

See you soon,

Maryline

I am interested in weak measures since I discovered this paper:

### Loading…

arxiv.org

I understood that retro-causality is only an interpretation and that's not more exploitable than the famous experiments of quantum gum delayed choice.

In fact, we don't control the result of the measurement, the correlations have always been made afterwards, and therefore, there is no communication as in the classical sense .

**In first**, we have a remarkable result, with correlations between strong measurements and weak measurements which**don't disturb the system**, but the counterpart is :**no control of the measure**.(We never control the measure, of course, but I continue my development)

Then, there is this famous Wheeler thought experiment like here :

https://en.wikipedia.org/wiki/Wheeler's_delayed-choice_experiment

*There is no way by which any given photon could have been determined to have arrived from one or the other of the double slits. However, if the detection screen is removed the wavefunctions on each path will superimpose on regions of lower and lower amplitudes, and their combined probability values will be much less than the unreinforced probability values at the center of each path.***When telescopes are aimed to intercept the center of the two paths, there will be equal probabilities of nearly 50% that a photon will show up in one of them. When a photon is detected by telescope 1, researchers may associate that photon with the wavefunction that emerged from the lower slit. When one is detected in telescope 2, researchers may associate that photon with the wavefunction that emerged from the upper slit**. The explanation that supports this interpretation of experimental results is that a photon has emerged from one of the slits, and that is the end of the matter.**Thus, secondly, the choice to measure**the wave behavior (screen) or the corpuscular behavior of light (telescope T1 or T2) seems to determine which slit passes the photon (F1, F2, or F1-F2), but the counterpart is :**no measurement possible upstream (directly in F1 or F2), otherwise we have a collapse of the wave function**.So I asked myself the question :

What would happen if we repeated Wheeler's famous thought experiment, (Gedankenexperiment as Einstein said) and that we decided to make the appropriate weak measures in F1 and F2, so as not to cause the collapse of the wave function ?

What would we get as results / correlations ?

I continued to search and I found this paper:

### Loading…

www.kiroku.riec.tohoku.ac.jp

I know there have been several debates in PF from that experience as here :

### A question about two-slits experiment

hello, I heard that in 2012 someone did an two-slits experiment in which they can detect which slit the photon passes without destroying the interference pattern. Is this news a fact or not ? if it is a fact, anyone could give me the paper to read ? thanks.

www.physicsforums.com

However, I didn't find the answer to my question that really more complex, so I decided to open a new discussion.

Indeed, I read the paper whose link was in the discussion :

### Loading…

www.tcm.phy.cam.ac.uk

I understood correctly :

*A strong measurement reveals a property of an individual system, but a weak measurement only reveals a property of a large statistical ensemble of equally prepared systems. A weak measurement says nothing about an individual system.*Ok

But my problem is this:

We all know that the probabilities of impact in a point if we observe in F1 or F2 are different from the probabilities of impact at the same point if we observe the screen :

P1 + P2 = |a1|² + |a2|²

is different from

P12 = |a1 +a2|²

(a = amplitude of probability)

__That's the question (finally !)__:**The average trajectories in the experiment should be different**, dependent that**we make**a strong measurement**or we don't make**a strong measurement, and thus**affect the weak measure**according**to the arbitrary choice of the experimenter to place a screen or not**.How to reconcile the no-go theorem with the strange possibility that BOB, which make a series of strong measurements (a screen = 1 or no screen = 0, throughout the series), can communicate with ALICE, which systematically make a series of weak measurements (slits), schematically of course, by using the protocol of the experiment described on the paper ?

(we can have a set of several ensemble of equally prepared systems simultaneously on the same table).

I admit that my question is difficult to ask and I often have trouble doing myself understood, so in advance, excuse me for this long post, (and my english !) but this problem don't let me sleep !

See you soon,

Maryline