# Observer Effect- Photon detectors, how do they work? Split from: Double Slit Experiment

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5 minutes ago, Itoero said:

T﻿he﻿ observer effect and﻿﻿ ...

Still irrelevant to the thread topic

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No, you do not affect the energy of a donkey when you observe it. I really don't think you should argue with swansont like you know what you talking about, when you know he's a working physicist and h

I think the subject is wider than that.

You can put a donkey in a box ( stall ), thereby fixing its position and momentum. If you try that with an electron, sometimes you find it outside the box. If the box is too small, fixing its posi

2 hours ago, Itoero said:

The observer effect and HUP are basically 2 constrains  on how we interpret/observe/study reality/nature. The measurement effect is only when you use measuring devices...the Observer effect in physics is mostly a measurement effect. You have several kinds of observer effects: https://en.wikipedia.org/wiki/Observer_effect

The Hawthorne effect (also referred to as the observer effect) is a type of reactivity in which individuals (this can be any kind off lifeform) modify an aspect of their behavior in response to their awareness of being observed. This is for example why placebo controlled clinical trials are 'invented'. Or why people often have to hide themselves and use strong lenses when they film wildlife….it's to prevent wildlife from changing its  behavior because it's observed.

How is this relevant? The problem is not that we don’t know what the observer effect is.

2 hours ago, Itoero said:

Another: In information technology, the observer effect is the impact on the behavior of a computer process caused by the act of observing the process while it is running.

In physics, the observer effect is the theory that simply observing a situation or phenomenon necessarily changes that phenomenon. This is often the result of instruments that, by necessity, alter the state of what they measure in some manner. In the double slit experiment,  the detectors and the screen are the instruments that alter the state of what they measure in some manner.  (like transforming energy and destroying wave behavior.

And yet it’s not the same thing as the HUP.

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3 hours ago, Itoero said:

In physics, the observer effect is the theory that simply observing a situation or phenomenon necessarily changes that phenomenon. This is often the result of instruments that, by necessity, alter the state of what they measure in some manner. In the double slit experiment,  the detectors and the screen are the instruments that alter the state of what they measure in some manner.  (like transforming energy and destroying wave behavior.

In the double slit experiment, an entangled particle is measured (possibly after the fact) and so the observer effect does not affect the particle that goes through the slits.

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21 hours ago, Strange said:

Still irrelevant to the thread topic

That's true but people say things which are wrong, regarding the observer effect. So it's imo necessary  to explain it.

19 hours ago, Strange said:

In the double slit experiment, an entangled particle is measured (possibly after the fact) and so the observer effect does not affect the particle that goes through the slits.

The observer effect affect the particles on the screen (it transforms energy). Do you deny this?

Why do you think an entangled particle is measured? They measure superposition, not entanglement.

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26 minutes ago, Itoero said:

That's true but people say things which are wrong, regarding the observer effect. So it's imo necessary  to explain it.

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1 hour ago, Itoero said:

The observer effect affect the particles on the screen (it transforms energy). Do you deny this?

I suppose you can call the destruction of a photon a rather extreme example of the observer effect. But it is still largely irrelevant to the dual slit experiment. This is caused by diffraction (in the classical case) and the non-locality of quantum effects (described by wave functions).

If you want to say that diffraction is an example of the observer effect because the waveform is affected by the slit passes through, then I would say you have extended the term so far as to render it meaningless. If every interaction is going to be labelled "observer effect" then we need a new term to describe the fact that we affect something when we try to make a measurement.

1 hour ago, Itoero said:

Why do you think an entangled particle is measured?

Because it is a way of determining which slit the photon when through without affecting it (a direct detection of the photon would destroy it and so we would never know if it formed an interference pattern or not).

Why do you think an entangled particle is measured?

1 hour ago, Itoero said:

They measure superposition, not entanglement.

They measure polarisation.

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19 hours ago, Itoero said:

That's true but people say things which are wrong, regarding the observer effect. So it's imo necessary  to explain it.

Yes, that is obvious...

Let's go to the basics. Imagine you have a picture: showing e.g. a mountain far away, and a flower on the foreground. Due to the big distance between the flower and the mountain they cannot be both sharp, and the photographer has chosen to have the flower sharp, and the mountains unsharp. E.g.:

Now imagine you want to make a photograph of this photograph. If you choose your focus completely wrong everything will be unsharp. This you could call the observer effect (not quite of course because you do not influence the picture by photographing it). But you can make the picture sharper: but whatever you do, you won't get the mountains sharp, because on that picture the mountains themselves are not sharp. And that is not due to your way of photographing. It is due the picture itself. And so it is with the HUP: it expresses a feature of the object in question itself, namely of a quantum particle. It has nothing to do with the way of measuring.

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1 hour ago, Eise said:

Now imagine you want to make a photograph of this photograph. If you choose your focus completely wrong everything will be unsharp. This you could call the observer effect (not quite of course because you do not influence the picture by photographing it). But you can make the picture sharper: but whatever you do, you won't get the mountains sharp, because on that picture the mountains themselves are not sharp. And that is not due to your way of photographing. It is due the picture itself. And so it is with the HUP: it expresses a feature of the object in question itself, namely of a quantum particle. It has nothing to do with the way of measuring.

Nice. +1

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On ‎2‎/‎12‎/‎2019 at 6:13 PM, swansont said:

They are not related. The HUP is an inherent property of nature. The observer effect depends on how you do a measurement. ﻿

This is wrong, you say many things like that. Physics implies what people say about  Nature via exp. evidence. You should not make assumptions regarding a model showing a property of Nature.

The observer effect is the theory that simply observing a situation or phenomenon necessarily changes that phenomenon. In many science fields people observe phenomena via measuring devices....so then it's rather a measurement effect.. you can discuss if a measurement is really an observer effect since you still have to observe/interpret the measurements.  Those phenomna which are observed can be anything...including a donkey.

Edited by Itoero
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46 minutes ago, Itoero said:

This is wrong, you say many things like that. Physics implies what people say about  Nature via exp. evidence. You should not make assumptions regarding a model showing a property of Nature.

No, it's not wrong.

46 minutes ago, Itoero said:

The observer effect is the theory that simply observing a situation or phenomenon necessarily changes that phenomenon.

Which is not what the HUP says. They are not the same thing.

46 minutes ago, Itoero said:

In many science fields people observe phenomena via measuring devices....so then it's rather a measurement effect.. you can discuss if a measurement is really an observer effect since you still have to observe/interpret the measurements.  Those phenomna which are observed can be anything...including a donkey.

And I think one would be hard-pressed to do a measurement of a donkey that had any significance from a QM aspect, and the HUP is a distinctly quantum phenomenon. Your own examples confirm that the HUP and observer effect are two different things.

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you know I always find it amazing how many people declare others wrong simply because it doesn't agree with their misguided view, when all it takes is less than 30 seconds of a google search to show that the statement is accurate.

Here is a set of references from that quick search.

"Historically, the uncertainty principle has been confused[5][6] with a somewhat similar effect in physics, called the observer effect, which notes that measurements of certain systems cannot be made without affecting the systems, that is, without changing something in a system. Heisenberg utilized such an observer effect at the quantum level (see below) as a physical "explanation" of quantum uncertainty.[7] It has since become clearer, however, that the uncertainty principle is inherent in the properties of all wave-like systems,[8] and that it arises in quantum mechanics simply due to the matter wave nature of all quantum objects. Thus, the uncertainty principle actually states a fundamental property of quantum systems and is not a statement about the observational success of current technology.[9] It must be emphasized that measurement does not mean only a process in which a physicist-observer takes part, but rather any interaction between classical and quantum objects regardless of any observer.[10][note 1] "

A little research on your part Itoero might be in order, you might just learn a few things. As I myself rarely trust wiki here is one of the peer reviewed studies it refers to  (reference 8)

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Itoero,

You fail to see 2 things:

Uncertainty is a basic principle for every kind of wave, not just in QM. A long sinusoidal wave has a pretty precise frequency, but is of course smeared out over a longer distance. So its position is not precise. It doesn't mean that we cannot determine it precisely, it is not precise. Opposite with a small wave packet (e.g. a sound bang): it has a pretty precise position, but not a precise frequency. See e.g. this illustration:

The wave packet is a combination of waves with different frequencies: this means the wave has no precise frequency. Just note that there is no reference to QM here at all. It is a fundamental property of waves. Two none-QM examples:

• An AM radio station that is not modulated, has a precise frequency, e.g.70 kHz. You do not measure a signal at e.g. 69 kHz. However, as soon as the signal is modulated, it looks like this:This causes a spread in frequency. On your radio, you can already receive the radio signal e.g. at 67 kHz, until 73 kHz. This is the reason that for AM the audio frequency is artificially reduced, to avoid that the spread becomes too big, and radio stations would disturb each other.
• Also on your AM radio: if a thunderstorm is approaching you can hear the lightning as a cracking sound. Interesting is that you hear them on any frequency, you do not have to tune in on exactly the frequency of the lightning. And why? Because such a short EM pulse really contains all frequencies. It is not that we cannot determine the frequency, the pulse has no precise frequency.

So the unsharpness of waves is a real effect, not an effect of us measuring it. And its effect is explained by Fourier analysis, which is a mathematical procedure, not some pure physical effect. If a natural phenomenon behaves like a wave, it will behave like the mathematics of waves.

The second thing you do not see is that the Schrödinger wave function is not a simple physical object: we cannot measure it. We can only measure particles arriving at some point. If we repeat our measurements, we can empirically determine what the square of the wave function is (it is the chance distribution of our measurements). But e.g. we cannot measure the phase of the wave function. And it also does not make sense: the Schrödinger wave function is a complex function, i.e. it has a imaginary component (square root of -1, such stuff...). So, to speak of a physical effect (as the observer effect is) on something that is not physical does not make sense.

And further I am astonished that several experts here (Swansont, Mordred, Studiot) and I tell you that you are wrong, give clear arguments for that view, and back them up with articles, and you still stick to your wrong view point.

PS Click on the links to see the graphs. I do not know why, but I saw them in my posting when I was writing the post,  now they are just links.

Edited by Eise
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10 hours ago, Mordred said:

It must be emphasized that measurement does not mean only a process in which a physicist-observer takes part, but rather any interaction between classical and quantum objects regardless of any observer.[10][note 1] "

A little research on your part Itoero might be in order, you might just learn a few things. As I myself rarely trust wiki...

Yet another way to look at this....

The distinction between classical and quantum objects is purely arbitrary. See e.g. Heisenberg cut.

Evidence of e.g. a macroscopic decoherence field or a consciousness/observer field has been looked for and not found.

When/where/if a measurement is made is therefor an arbitrary choice, generally based on convenience.

18 hours ago, Itoero said:

The observer effect is the theory that simply observing a situation or phenomenon necessarily changes that phenomenon.

Since measurement/nonmeasurement is arbitrarily defined, any observation effect during measurement would have to be nonexistent to be consistent with measurements.

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8 hours ago, Eise said:

Uncertainty is a basic principle for every kind of wave, not just in QM

HUP is about phenomena with momentum/position. That's not necessary about QM, Physics or science...Most of what we observe has momentum/position.

Isn't entropic uncertainty a principle of a wave? I've read some papers that said how HUP is too basic, entropic uncertainty basically upgrades HUP.

8 hours ago, Eise said:

And further I am astonished that several experts here (Swansont, Mordred, Studiot) and I tell you that you are wrong, give clear arguments for that view, and back them up with articles, and you still stick to your wrong view point.

My view point is that HUP and observer effect is not necessary about physics or science  I backed it up and, explained it.

Another viewpoint is that HUP, indeterminism in QM, bell's theorem implies what we say about Nature.Physics doesn't say what/how Nature is, it implies what people say about Nature. Many people do think physics shows how Nature is, also the ones that write/wrote articles about it.

23 hours ago, swansont said:

, it's not wrong.

You said HUP is a property of Nature...this is wrong, but you deny it?

On ‎2‎/‎19‎/‎2019 at 6:22 PM, swansont said:

Which is not what the HUP says. They are not the same thing.

Of course they are not the same, I did not say they are.

On ‎2‎/‎19‎/‎2019 at 6:22 PM, swansont said:

And I think one would be hard-pressed to do a measurement of a donkey that had any significance from a QM aspect, and the HUP is a distinctly quantum phenomenon. Your own examples confirm that the HUP and observer effect are two different things﻿.

HUP is not a quantum phenomen.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1262781/

When you observe a donkey  there can be an observer effect. And you can't measure its position and momentum precise at the same time....when the donkey is on the move.

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5 minutes ago, Itoero said:

HUP is about phenomena with momentum/position. That's not necessary about QM, Physics or science...Most of what we observe has momentum/position.

Isn't entropic uncertainty a principle of a wave? I've read some papers that said how HUP is too basic, entropic uncertainty basically upgrades HUP.

My view point is that HUP and observer effect is not necessary about physics or science  I backed it up and, explained it.

Another viewpoint is that HUP, indeterminism in QM, bell's theorem implies what we say about Nature.Physics doesn't say what/how Nature is, it implies what people say about Nature. Many people do think physics shows how Nature is, also the ones that write/wrote articles about it.

You said HUP is a property of Nature...this is wrong, but you deny it?

Of course they are not the same, I did not say they are.

HUP is not a quantum phenomen.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1262781/

When you observe a donkey  there can be an observer effect. And you can't measure its position and momentum precise at the same time....when the donkey is on the move.

No, you do not affect the energy of a donkey when you observe it. I really don't think you should argue with swansont like you know what you talking about, when you know he's a working physicist and has likely forgotten more than you and I know.

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24 minutes ago, Itoero said:

HUP is about phenomena with momentum/position. That's not necessary about QM, Physics or science...Most of what we observe has momentum/position.

The HUP applies to any non-commuting variables. It does not apply to ones that commute.

24 minutes ago, Itoero said:

HUP is not a quantum phenomen.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1262781/

When you observe a donkey  there can be an observer effect. And you can't measure its position and momentum precise at the same time....when the donkey is on the move.

“We have presented here the first uncertainty principle to be announced in structural genomics. This is an addition to the uncertainty principles in physics”

So, not the same thing

also “in his 1927 article Werner Heisenberg insisted that the uncertainty he described is not due to technical or intrinsic features of the measuring process, but it is a fundamental feature of reality itself, i.e. an electron cannot in principle have a precise position and momentum simultaneously”

IOW, your citation disagrees with you

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35 minutes ago, Itoero said:

The Heisenberg uncertainty principle is very specifically about pairs of observables in quantum theory.

36 minutes ago, Itoero said:

You﻿﻿ said HUP is a property of Nature...this is wrong, but you deny it?﻿﻿﻿

What would it be a property of, if not nature?

37 minutes ago, Itoero said:

That is an "uncertainty principle" in genetics inspired by the Heisenberg uncertainty principle. The Heisenberg uncertainty principle is only a quantum phenomenon.

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1 hour ago, Strange said:

The Heisenberg uncertainty principle is very specifically about pairs of observables in quantum theory.

I think the subject is wider than that.

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27 minutes ago, studiot said:

I think the subject is wider than that.

Can you tell me what the video is about? Is there a readable source?

And is this "more general uncertainty principle" the same as or different from the Heisenberg uncertainty principle?

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13 minutes ago, Strange said:

Can you tell me what the video is about? Is there a readable source?

And is this "more general uncertainty principle" the same as or different from the Heisenberg uncertainty principle?

1 hour ago, swansont said:
2 hours ago, Itoero said:

HUP is about phenomena with momentum/position. That's not necessary about QM, Physics or science...Most of what we observe has momentum/position.

The HUP applies to any non-commuting variables. It does not apply to ones that commute.

Non commutating variables (operators) mean that if you apply a then B you get a different answer from if you apply B first then A

[BA - AB ] is known as the commutator and can be linked to the diffraction pattern in slit experiments.

If [BA - AB ] = 0 then that is another way of saying the variables commute.

Interestingly, the variables may commute in one direction, but not another.

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1 hour ago, studiot said:

I think the subject is wider than that.

I managed to watch the introductory bit of that. It seems to confirm that the Heisenberg uncertainty principle is a specific example of an uncertainty principle, that applies specifically to quantum variables. Does it contradict that later?

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Right at the beginning he starts by discussing uncertainty in classical systems.

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27 minutes ago, studiot said:

Right at the beginning he starts by discussing uncertainty in classical systems.

Yes. Obviously.

But you said that the Heisenberg uncertainty principle is not a purely quantum thing. That is what I am trying to understand. Does the video show that the  Heisenberg uncertainty principle applies to classical systems?

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1 hour ago, Strange said:

Yes. Obviously.

But you said that the Heisenberg uncertainty principle is not a purely quantum thing. That is what I am trying to understand. Does the video show that the  Heisenberg uncertainty principle applies to classical systems?

Did I ?

I thought I said that the subject was not purely quantum.

Heisenberg was certainly (pun intended) aware of classical uncertainties when he developed his application of uncertainty to QM.

2 hours ago, studiot said:
4 hours ago, Strange said:

The Heisenberg uncertainty principle is very specifically about pairs of observables in quantum theory.

I think the subject is wider than that.

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5 hours ago, studiot said:

I think the subject is wider than that.

Excellent video, its extremely elegant in describing the measurement uncertainty of any wavefunction in terms of the  Fourier transforms.  The main point is that any wavefunction has inherent uncertainties that have nothing to do with observation interference. Particularly since all particle states in QM and QFT are indeed wavefunction typically simplified in representation to $|\psi\rangle$ believe me unless you have an intensive study merely describing how that is defined via the boson creation and annihilation operators is daunting at best.

as you can see

the position and momentum are the operators used to define the creation and annihilation operators under QM so these formulas will be different than in QFT treatment.  where the position operator is replaced with the field operator. The previous uses the Schrodinger equation while under QFT its the Klein Gordon equation (these are the two primary distinctive differences between QM and QFT FYI )

Edited by Mordred

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