What is Decoherence?

originally posted by: HotMale


"How did they detect the path of the particle?" - Imafungi


With a device.

It is possible some devices result in interference and some do not when used to detect paths of particles, but we can leave this statement on the back burner.

But yes, ok, this is the classic, 'the device makes the particle choose a path'.

What does the device do to detect the path of the particle, and how is the particle effected by the device?

Is the interference pattern existing/detected, when the path is not detected? With a single atom? interference pattern, with out detecting the path the atom took?

a reply to: ImaFungi

Is the interference pattern existing/detected, when the path is not detected? With a single atom? interference pattern, with out detecting the path the atom took?

Yes, with a single atom without detecting path.

originally posted by: HotMale

"Is the interference pattern existing/detected, when the path is not detected? With a single atom? interference pattern, with out detecting the path the atom took?" - Imafungi


Yes, with a single atom without detecting path.

Can you quote the source or statements which proves, evidences this?

That a single atom enters, and an interference pattern is detected, without any detection in the path, without any energy entering the apparatus, besides the single atom.

a reply to: ImaFungi

What is confusing you? This is basic Quantum Physics, no detection of path= interference pattern, detection of path= non interference pattern. Or is it the use of a single particle that is unexpected to you?

The experiment from the other thread, for instance. You know the one you participated in......

It's a slight variation from what you were asking for, but it boils down to the exact same thing. There are other variations of the Eraser experiment I can post, cause I fully expect you to take this out of context.

gadgets.ndtv.com...

Truscott's team first trapped a collection of helium atoms in a suspended state known as a Bose-Einstein condensate, and then ejected them until there was only a single atom left. The single atom was then dropped through a pair of counter-propagating laser beams, which formed a grating pattern that acted as crossroads in the same way a solid grating would scatter light. A second light grating to recombine the paths was randomly added, which led to constructive or destructive interference as if the atom had travelled both paths. When the second light grating was not added, no interference was observed as if the atom chose only one path.

Mind you the light gratings are not the detectors, the path detectors are at the end of the paths created by the light gratings. They randomly add the second light grating which makes it impossible to determine which path it came from, effectively erasing the info, creating an interference pattern, as if it took both paths. If they don't the path is determinable, creating a non interference pattern.

There are different variations of this experiment all with the same results and implications.

a reply to: trifecta

This whole thread gives me a migraine...Physics was never my first love; but I persevere trying to understand or catch glimpses.

Photons are thought to carry information.

DNA and Biophotons
www.greenmedinfo.com...

Our Cells and DNA Use Biophotons To Store and Communicate Information
Apparently biophotons are used by the cells of many living organisms to communicate, which facilitates energy/information transfer that is several orders of magnitude faster than chemical diffusion. According to a 2010 study, "Cell to cell communication by biophotons have been demonstrated in plants, bacteria, animal neutriophil granulocytes and kidney cells."[9] Researchers were able to demonstrate that "...different spectral light stimulation (infrared, red, yellow, blue, green and white) at one end of the spinal sensory or motor nerve roots resulted in a significant increase in the biophotonic activity at the other end." Researchers interpreted their finding to suggest that "...light stimulation can generate biophotons that conduct along the neural fibers, probably as neural communication signals."

originally posted by: Arbitrageur
a reply to: Kashai
Can the hypothetical android "Data" from Star Trek have knowledge? Does it have consciousness?
Can the Geiger counter have knowledge of the radioactive decay event?
Where between the Geiger counter, the android or other AI and a human do you draw the line if there is one?

You can get into a game of semantics and philosophy that is beyond the scope of science. In some sense of the definition of knowledge the Geiger counter has knowledge of the decay event. That's what's relevant to this thread about decoherence.

The other thread "Quantum Experiment Confirms Reality Doesn't Exist Until Measured" is where the OP tries to make a case for this "consciousness required", but it's really just a tautology to say that only a conscious observer can make a conscious observation. It's like saying the reason my car is blue is because it was painted blue. While it may be true to make such claims they are far from useful. The Geiger counter doesn't need consciousness to record the decay event so consciousness is irrelevant to decoherence.

The existence of human life on Earth is not semantics or philosophy. It is the only reason fire was controlled or the measurement problem is acknowledged as a problem. The fact that you have a blue car is impossible without human intervention.

The fact we are having this conversation is due to the fact that we figured out something. That is not observable with the common senses and in and of itself well beyond anything classical thinking even imagined was possible at the time.

Decoherence /ˌdiːkəʊˈhɪərəns/
noun
1. (physics) the process in which a system's behavior changes from that which can be explained by quantum mechanics to that which can be explained by classical mechanics

Source

So despite the fact their is no Unified field theory what exactly are you trying to say????

Any thoughts?

originally posted by: HotMale


What is confusing you? This is basic Quantum Physics, no detection of path= interference pattern, detection of path= non interference pattern. Or is it the use of a single particle that is unexpected to you?

I have never seen any evidence or literature or speak of a single atom creating an interference pattern.

"Truscott's team first trapped a collection of helium atoms in a suspended state known as a Bose-Einstein condensate, and then ejected them until there was only a single atom left. The single atom was then dropped through a pair of counter-propagating laser beams, which formed a grating pattern that acted as crossroads in the same way a solid grating would scatter light. A second light grating to recombine the paths was randomly added, which led to constructive or destructive interference as if the atom had travelled both paths. When the second light grating was not added, no interference was observed as if the atom chose only one path."

Yep, hokus pokus guess work. There are multiple laser beams involved in this... this is garbage.


A single atom, always only takes one path. The interference pattern is never the result of only a single atom.

Why is it that the conclusion exits that human simplicity can be applied to reality?

a reply to: ImaFungi

Physicists have just upped their ante: Not only have they split atoms but, even trickier, they've put them back together.

Their secret? Quantum physics. A team of scientists was able to "split" an atom into its two possible spin states, up and down, and measure the difference between them even after the atom resumed the properties of a single state.

Source

originally posted by: ImaFungi
A single atom, always only takes one path.

If the deBroglie-Bohm interpretation is correct this is true but we don't know if it is correct. It's not a very popular interpretation of quantum mechanics but as far as I know nobody has proven this or the other main interpretations wrong.

The interference pattern is never the result of only a single atom.

What you can calculate for a single particle is a probability plot of where the particle will be measured. The probability plot is like an interference pattern with peaks and valleys, so in some sense even a single particle is following this probability plot showing the interference.

If you are saying the pattern itself doesn't emerge until you've repeated this experiment with more particle, that is true, however this glosses over the fact that the predicted location of each single particle does follow an interference pattern and experiment proved this prediction correct.

It's kind of like saying the probability of rolling snake eyes with two dice is one in twelve. You can't prove this probability with a single roll of the dice. However that doesn't mean the probability of snake eyes is not 1 in 12. The very nature of probability is that probabilities can't be confirmed with a single data point.

If you roll the dice 1200 times and get snake eyes 100 times, it sure looks like that 1 in 12 probability is correct. It is in that sense the interference pattern is built into the probability predictions for a single particle interfering with itself, because as with the dice, if you fire 1200 particles one at a time, you will see the interference pattern emerge which is only explainable if each particle is in some sense interfering with itself, unless you have a better explanation.

a reply to: neoholographic

Sheesh OP... haven't you gotten tired of debating this issue yet? Well neither have I... so lets continue lol.

When an observer interacts with the video he will see a cat get killed on the tape or a cat survive. Until that happens, the cat and the camera is a two state system. How can decoherence occur without an outside observer interacting with a state of the cat in the box?

You need to explicitly define what an observer is. You are implying that only conscious beings can act as an observer and make measurements but that's simply not true. The camera its self can act as an observer without anyone ever needing to look at it. This can be proven very simply by setting up the double-slit experiment and placing a detector on one of the slits, you'll find that the interference pattern disappears whether or not you look at the result of the detector to discover which slit the particle went through. The detector its self acted as the observer and collapsed the wave-function because the detector is a large macroscopic object with a high energy and high complexity.

If you have a system in a box like a cat that isn't interacting with the outside environment, how can decoherence occur???? IT DOESN'T EXPLAIN WHAT AN OBSERVATION ACTUALLY IS.

For a start, the box the cat is in will act as an environment which the cat can become entangled with. The "outside environment" doesn't need to be a huge forest, it just needs to be large enough to cause decoherence when entangled with the cat. But even the cat its self is a high energy object and it's not in a wave-state the same way an elementary particle is when we aren't looking at it. That is also why the moon is still there even when no one is looking at it.

Why decoherence solves the measurement problem (2013)

The solution of the quantum measurement problem, entirely within conventional quantum physics, has been published on at least four occasions (Scully, Shea, & McCullen, 1978; Scully, Englert, & Schwinger, 1989; Rinner & Werner, 2008; Hobson, 2013) . A similar solution has been presented by (Dieks, 1989; Dieks, 1994; Lombardi & Dieks), who propose it as a fundamental postulate that amounts to a new "modal interpretation" of quantum physics. Yet many articles in this and other journals continue to treat measurement as an unsolved fundamental problem whose resolution requires either exotic interpretations or fundamental alterations of quantum theory. For example, Adler (2003) has published an article titled "Why decoherence has not solved the measurement problem," despite the fact that, as will be reviewed below, decoherence has solved the measurement problem.

originally posted by: ImaFungi
What does the device do to detect the path of the particle, and how is the particle effected by the device?

Well you may or may not find this interesting but I have a hypothesis on how this may work. This is mainly just a reposting of stuff I recently posted while debating neo in another one of his threads but I've put it all together into this one post to make it a bit easier to follow. My core argument is that measurements don't have to be made by conscious beings, they can also be made by non-conscious objects, and we have ample experimental evidence to support this claim.

Let us define a measurement as one high energy system (machine, human, etc) interacting with a low energy system in superposition (elementary particle, qubit, etc). There is no way to make a measurement of an elementary particle without interacting with the particle and becoming entangled with the particle. The particle will then take on properties of the high energy system because the entanglement will cause the wave function of each subsystem to merge. Large objects don't exhibit weird quantum behavior because they have an extremely high energy/frequency wave function.

It is extremely hard to make quantum computers because the qubits become entangled with their environment and the decoherence causes them to start acting in a classical way. The qubit will start to take on the classical properties of its environment the longer it is allowed to interact with the environment because its wave function will leak out and merge with the surrounding systems. If a human tries to measure the state of the qubit it will also start exhibiting classical behavior because humans are high energy objects and we are well defined in reality.

I like the term "well defined" because that's how I really like to think of decoherence. Very small and simple systems such as elementary particles are not well defined and therefore they exhibit particle-wave duality. But if we try to interact with those ill defined systems we force them to become well defined. Another way to think of it is in terms of entropy. The structure of a human is highly complex and requires a lot of information to describe, but an elementary particle requires much less information to be described and so it's definition is much less specific.

In some sense a low entropy system is "less real" because it's ill defined and it's existence is not even certain. But high entropy system such as humans don't question their own existence, reality seems very solid and static from our frame of reference, it seems to be very well defined, we don't see large objects assuming states of superposition. When a low entropy system such as an elementary particle becomes entangled with a high entropy system such as a machine or human they become part of the same system and share the same level of entropy.

In other words the process of entanglement allows the particle to acquire some of the "realness" of the high entropy system it has become entangled with and thus it begins to act like a classical particle instead of a wave of probability. Or to put it another way, the observer leaks "realness" into the particle by becoming entangled with it. I know that's probably not the best terminology but I think it's actually very close to the truth. It may not be clear what I mean by entropy, what I'm really talking about is Shannon entropy.

If you wrote a novel and then you tried to compress the text of that novel as much as you possibly could, you would compress the original text until it looked like a totally random string but you would not be able to compress it any further than that. If I was trying to pack the maximum amount of information I possibly could into this post then it would look completely random, and the more random it is, the more entropy it has. This is why we call a source of random numbers a source of entropy in computing.

The complexity of any given finite system is a measure of how much information is required to describe everything about the system. The amount of information you are left with after compressing the information as much as possible defines the level of complexity. A string containing the same character repeated a billion times can obviously be defined with a small amount of information and thus it can be said to have a low complexity compared to a totally random string of the same length.

The type of complexity I'm talking about is called Kolmogorov complexity. If I have a string of characters then the Kolmogorov complexity of the string can be measured as "the length of the shortest possible description of the string in some fixed universal description language". As entropy increases the complexity will increase because random systems are harder to define than systems which contain patterns that are easy to compress. This is why highly complex objects have a high entropy.

Another good example which the wiki mentions is the Mandelbrot set. Even though Mandelbrot fractals looks extremely complex they can actually be generated with a rather simple algorithm. So the amount of information required to define a Mandelbrot fractal is actually rather small. But if you have just a randomly generated image and you try to create an algorithm which will replicate that image you will find yourself writing a rather long algorithm because a random image has a high level of entropy and therefore a high level of complexity.

Simple objects such as elementary particles are much easier to define because they are less complex, meaning less information is required to define an elementary particles compared to a chemical element which is a collection of elementary particles. Kolmogorov complexity is exactly the type of complexity I'm talking about, it is dictated by the minimum amount of information required to describe an object such as a string or a particle.

Low complexity systems require less information to be defined, even their exact position isn't well defined, so in some sense they are less real than systems which require a lot of information to be described. There is no reason this concept cannot be extended beyond elementary particles and chemical elements, we can consider larger objects including humans. Obviously we aren't perfectly isolated from our environment and so we aren't a closed system, but it's still possible to approximate the number of particles, etc.

a reply to: ImaFungi

I have never seen any evidence or literature or speak of a single atom creating an interference pattern.

Just goes to show how knowledgeable you are.You obviously hadn't even reviewed the experiment you were "discussing" in the other thread.

Well you have seen it now. Oh let me guess, you are simply going to deny it because it doesn't fit your preconceived notions.

Yep, hokus pokus guess work. There are multiple laser beams involved in this... this is garbage.

See just as expected.

You really don´t have a clue do you?

The laser beams just form a path, they are not interacting with the particle. If they were we would always see an interference pattern in the case of this set up but we only see it when the second grating is added. If it only travels through the first grating there is no interference pattern. In both cases it traveled through a light grating. The only difference is availability of path info.

Furthermore this setup is reversed. Normally the argument would be that the interference pattern collapsed because something was introduced into the system. Normally, the argument from your side is that the interference pattern collapsed because of the measuring device measuring the path or whatever other interaction.

In this case, we see an interference pattern when something is added to the system, namely the second light grating.

This alone disqualifies that whole argument that interference patterns collapse when you add something to a system.

It clearly shows that only variable is availability of path info.

This whole notion that all quantum results are due to inherent flaws in the experimental setups is prepostrous. If this is the case there would be nothing to see here and no reason to keep conducting these experiments.

A single atom, always only takes one path. The interference pattern is never the result of only a single atom.

You are completely ignorant of experimental results and their implications and the basics of Quantum Physics in the first place.

I am really done with you.

a reply to: ChaoticOrder

You need to explicitly define what an observer is. You are implying that only conscious beings can act as an observer and make measurements but that's simply not true. The camera its self can act as an observer without anyone ever needing to look at it. This can be proven very simply by setting up the double-slit experiment and placing a detector on one of the slits, you'll find that the interference pattern disappears whether or not you look at the result of the detector to discover which slit the particle went through. The detector its self acted as the observer and collapsed the wave-function because the detector is a large macroscopic object with a high energy and high complexity.

This is what I have been saying about "path info AVAILABILTY". It doesn't matter if you look which path it actually took, what matters is the AVAILABILITY of such info.

This is what I have been pointing out with these eraser experiments. When you "erase" the path info, making it UNAVAILABLE, you get an interference pattern, when it is AVAILABLE the interference pattern collapses. That's the whole point. In both cases there was detection by a detector. Only in the case where the info is available does the interference pattern collapse.

This shows it is not the detector itself causing it but the AVAILABILITY of info.

Why would it matter wether or not the info is AVAILABLE if the conscious observer plays no role?

The reason the interference pattern collapses even if you don't look at the info of the detection, is because there is a potential that you are going to look at it.

What if you got an interference pattern and then decided to look at the detection and you learned the path info?

Reality wouldn't be correct then would it?

a reply to: ChaoticOrder

Large objects don't exhibit weird quantum behavior because they have an extremely high energy/frequency wave function.

Macroscopic objects don't exhibit weird quantum behavior because they are not in an experimental environment where particles are presented with a choice.

Off course we don't see weird quantum behavior in the macroscopic world. In order to understand macroscopic reality we have to look at its building blocks, particles.

It is when we subject these particles to an unnatural environment that we see an inner mechanism at work.

These quantum experiments don't show the normal workings of reality but they show that there is something at work behind the scenes that in this case is making sure that reality is "correct" in a set up that provides reality with the option of not being "correct".

It's poking reality with a sharp stick then seeing it making all kinds of weird leaps to get away from it.

a reply to: Arbitrageur

if you fire 1200 particles one at a time, you will see the interference pattern emerge which is only explainable if each particle is in some sense interfering with itself, unless you have a better explanation.

Agreed. So if you believe this how can you believe that the conscious observer does not play a role?

The ongoing argument against this idea is that it is not the act of conscious observation, but the physical interaction of a measuring device with a particle that collapses the interference pattern.

Besides that this is disproven by Eraser experiments, this argument can not be seen as valid if you believe that the interference is caused by the particle interfering with itself because it takes both paths.

When does it not take both paths?

When you observe and the path info is available. It can't interfere with itself if there is proof that it took one of the paths.

So knowing all this, how can you still deny the role of the observer?

a reply to: HotMale

No they do show the normal workings of reality just on diffrent scales. The thing you don't seem to be getting is that the only way we know anything at all exists is by its effect on other things. Any observations we make in the real world require interactions to occur we can't directly see or observe.Let's say I paint a wall green. When we observe it we see a green wall. Get closer to the wall using a microscope and now we see the green wall is individual paint chips with a green tint. Now let's get closer now we see the atoms that make up the paint chips they are moving constantly at this point we No longer see our green wall. This is physics the smaller the area we look the more we see properties that we were not aware of. This is the macroscopic world.

Now I see several on here are confusing to diffrent theoriesCopenhagen interpretation at its most basic says that all the subatomic particles that make up the universe can and should be thought of as wavefunctions, which are probabilistic representations of a particle's location and velocity at any given time. Measuring or observing these particles is what causes them to collapse into only one of all possible values this is what we call a wavefunction collapse. In this interpretation everything in the iniverse is a wave function including matter.

Now the secondThe other idea was first put forward by Hugh Everett in 1957. He kept most of the Copenhagen interpretation but removed one crucial part: the wavefunction collapse. Without it, all probabilistic values for every subatomic particle would exist in superposition, all at once. In theory, this meant that was a very large and quite probably infinite number of universes in parallel existence.This tells us each interaction branches off another universe this is where superposition comes in our particle can be in two places well in fact millions and billions of places at once. Probabilities play the role of keeping our universe with some sort if consistency.

Now on here people have been freely mixing these two versions. And it leads to alot of misinterpretation of results.superposition doesn't prove reality doesn't exist and the collapse of a wave function in no way means reality isn't real by the Copenhagen interpretation it just verifies everyrhing in the universe is a wave function. Now pick one or the other but let's keep them seprate because it makes it look like we our waffling between answers. The OP is clearly talking about the many world's interpretation with the explination of decoherence.

a reply to: dragonridr

No they do show the normal workings of reality just on diffrent scales. The thing you don't seem to be getting is that the only way we know anything at all exists is by its effect on other things. Any observations we make in the real world require interactions to occur we can't directly see or observe.Let's say I paint a wall green. When we observe it we see a green wall. Get closer to the wall using a microscope and now we see the green wall is individual paint chips with a green tint. Now let's get closer now we see the atoms that make up the paint chips they are moving constantly at this point we No longer see our green wall. This is physics the smaller the area we look the more we see properties that we were not aware of. This is the macroscopic world.

No it is not the normal working that is shown in these experiments. And why are you ignoring the points I made. In macroscopic reality particles are not subjected to closed environments where they can choose different paths and can be followed or are setup so that apparent time paradoxes arise.

And I clearly said that in order to know more about the macrsocopic world we have to look at its building blocks.

The rest of your post is still ignoring all the results I have been posting about in detail, but what else is new.

Now on here people have been freely mixing these two versions. And it leads to alot of misinterpretation of results.superposition doesn't prove reality doesn't exist and the collapse of a wave function in no way means reality isn't real by the Copenhagen interpretation it just verifies everyrhing in the universe is a wave function. Now pick one or the other but let's keep them seprate because it makes it look like we our waffling between answers.

Here this, these are gross oversimplifications of experimental results, leaving out the key factors of these experiments that give these results their meaning.

None of you guys seem even able to adress the proper issues. Is it paradigm bias or are you all just incapable of recognising the implications of things? Or both?

originally posted by: HotMale
a reply to: dragonridr

No they do show the normal workings of reality just on diffrent scales. The thing you don't seem to be getting is that the only way we know anything at all exists is by its effect on other things. Any observations we make in the real world require interactions to occur we can't directly see or observe.Let's say I paint a wall green. When we observe it we see a green wall. Get closer to the wall using a microscope and now we see the green wall is individual paint chips with a green tint. Now let's get closer now we see the atoms that make up the paint chips they are moving constantly at this point we No longer see our green wall. This is physics the smaller the area we look the more we see properties that we were not aware of. This is the macroscopic world.

No it is not the normal working that is shown in these experiments. And why are you ignoring the points I made. In macroscopic reality particles are not subjected to closed environments where they can choose different paths and can be followed or are setup so that apparent time paradoxes arise.

And I clearly said that in order to know more about the macrsocopic world we have to look at its building blocks.

The rest of your post is still ignoring all the results I have been posting about in detail, but what else is new.

Now on here people have been freely mixing these two versions. And it leads to alot of misinterpretation of results.superposition doesn't prove reality doesn't exist and the collapse of a wave function in no way means reality isn't real by the Copenhagen interpretation it just verifies everyrhing in the universe is a wave function. Now pick one or the other but let's keep them seprate because it makes it look like we our waffling between answers.

Here this, these are gross oversimplifications of experimental results, leaving out the key factors of these experiments that give these results their meaning.

None of you guys seem even able to adress the proper issues. Is it paradigm bias or are you all just incapable of recognising the implications of things? Or both?

It's YOU THAT IS misinterpreting results. And intermingled theories. Pick one and will discuss if you want to discuss decoherence fine then we look at the many world's interpretation to prevent those pesky time paradoxes as you mentioned. But then discussing wave functions is useless endeavor. As I said pick one or the other and I'll be happy to go over it with you. I have students all the time when they first get into physics mix these two.

a reply to: dragonridr

I think you can find what I posted if you actually want to discuss results instead of meaningless blabber.

Is it supposed to mean something to me that you have students?

It's YOU THAT IS misinterpreting results.

Whatever, you are completely ommitting key factors from these experimental results.