Is the Measurement Apparatus made up partly of electrons? Perhaps not.

In summary, the conversation is discussing the relationship between quantum theory and microscopy, specifically regarding the measurement problem and the nature of measurement apparatus. One perspective is that the apparatus is made up of classical macroscopic objects, while another suggests it is made up of quantum microscopic objects. However, according to quantum mechanics, it is not possible to say definitively that the measurement apparatus is made up of electrons. At the most fundamental level, all matter is made up of quarks, leptons, and bosons, but the challenge is understanding how the behavior of matter at a larger scale can be derived from this fundamental knowledge. This is a complex topic in theoretical physics.
  • #1
lucas_
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This is related to the thread "Is quantum theory a microscopy theory?" discussed mostly by Ph.Ds. I make this new thread so as not to disturb the experts discussions or even hijack or close it prematurely.

In message #27 of https://www.physicsforums.com/threads/is-quantum-theory-a-microscopic-theory.974961/page-2 atty said:

"It is intimately related to the measurement problem. The quesstion remains even if one is able to use terms like classical microscopic, classical macroscopic, quantum microscopic, quantum macroscopic. Is the measurement apparatus (classical macroscopic) made of electrons (quantum microscopic)?"

I guess the reason the question whether measurement apparatus is made of electrons is valid is because if electrons were wave functions that are not physical but only detecting purposes. Then apparatus is not made of electrons, right? This was what atyy meant, right?

Or let's use more accurate description. We know in childhood dogma that measurement apparatus is made of atoms. But since atoms and electrons are in the same company being microscopic quantum objects. If the wave function is not real or doesn't represent something real and it is just for calculation purposes for the output. Then the question:

Is measurement apparatus made up of atoms?

can be answered by say "No. Measurement apparatus is not made up of atoms, but made up of little pink elephants. But we can't detect the little pink elephants, we can only detect the detection events, and these are what the wave functions or particles like "electrons" simply are.".

Was this what atyy was implying?

There is many deep subtleness in the question so please read the main thread "Is quantum theory a microscopy theory?" for context as all this is related to it. Independently, all my questions above may sound absurd but it is related to the discussions of the main expert thread.
 
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  • #2
So is the following correct if I'd write a pop-sci article that begins something with (given the context of the first message):

"It is established fact that tables and chairs were made of atoms as we were taught in high school. But hidden in isolated corners in many parts of the world, numerous top physicists with Ph.D. doubt tables were really made of atoms and electrons. Some believe atoms and electrons were just concepts for measurements and detections. In other words, they are only in our mind and calculators. What matter really are is still a mystery. They could be made up of little pink elephants or something more exotic".

The above pun is correct, right? It may be obvious to the experts. But being-non expert. Please tell me which part of the concept may be a mistake before I write it in Discover magazine. Thank you.
 
  • #3
Basically when you use QM the device is treated in a special way by the formalism as purely classical "as if" it was not made of electrons and other quantum particles. Exactly why this is and the details of it are a bit subtle and a large part of Bohr's essays, so I'll only go into it if you wish.

However you can zoom out and treat the device as being made of atoms like it really is. Once again though you will invoke another classical device.

So there will always be something you treat "as if" it wasn't made of atoms.
 
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  • #4
DarMM said:
Basically when you use QM the device is treated in a special way by the formalism as purely classical "as if" it was not made of electrons and other quantum particles. Exactly why this is and the details of it are a bit subtle and a large part of Bohr's essays, so I'll only go into it if you wish.

Let's ignore Bohr's need for classical measuring device to set the preferred basis. Let us treat everything as quantum. Here are tables made up of atoms and electrons?

Why did atyy say:

"TeethWhitener said: So does it even make sense to talk about a purely classical microscopic theory?

Atyy: "No, since we would like to say the classical measurement apparatus is made of electrons, which are quantum. However, quantum mechanics does not seem to allow us to say that."

Reference https://www.physicsforums.com/threads/is-quantum-theory-a-microscopic-theory.974961/page-2

So quantum mechanics does not allow us to say that measurement apparatus is made of electrons?

However you can zoom out and treat the device as being made of atoms like it really is. Once again though you will invoke another classical device.

So there will always be something you treat "as if" it wasn't made of atoms.

Let's not zoom out or think classically. Let's think quantumly all the way.
 
  • #5
I think this is a very good question, and indeed to our current knowledge, everything around as (as far as we know it, and that's only about 4% of all available entities which provides energy, momentum, and stress in the universe!) is made up of quarks, leptons, Higgs bosons ("matter") and a bunch of socalled gauge bosons (gluons, photons and W and Z bosons). All of these are described as quantized fields. This, however is just the picture on the most fundamental level, and it is also a valid description only when looked at matter at very high resolution, i.e., if it is probed with high-energy particles (or photons).

This is, however, only one (in some sense the easy) part of our understanding: It's just looking close enough in the attempt to resolve the matter at the smallest level of resolution. It's far from the behavior of matter as we know it in daily experience. The good thing is, we know with quite some accuracy of this most fundamental level, what the constituents of matter are (listed above) and how they interact in terms of a relativistic quantum field theory known as the "Standard Model".

The challenge now is to understand how the behavior of matter surrounding us may be somehow derived from this fundamental knowledge neatly summarized in the "Standard Model". This works at different levels of ever coarser resolution, and this is the complicated piece of theoretical physics!

The first level is to understand "hadrons". These are, very simplified, bound states of three quarks (baryons) or a quark and an anti-quark (mesons) and also some more "exotic" multi-quark states. This is not so easy because of the feature of QCD to be "confining", which means that quarks (and gluons) are always confined in colorless (hadronic) states, and this is a non-perturbative phenomenon. Perturbation theory only works at low coupling constants, and for QCD the coupling constants get large at low energies. The only way we have today is to evaluate certain aspects of QCD on the computer using lattice-QCD simulations. Among other things one can calculate the masses of the hadrons, and one gets the correct answers for the known hadrons quite well. That's why, among other successes, one believes that indeed QCD, the strong-interaction part of the Standard Model, is the correct description of the strong nuclear force.

On the next level we have atomic nuclei, i.e., bound states of protons and neutrons as the only "stable" baryons, though a free neutron decays due to the weak interaction in a ##\beta## decay, but still within the stable nuclei it's stable as well. The nuclear properties can be rather well understood using many-body QT using effective interactions between protons and neutrons, which can also at least partially derived from effective hadronic field theories based on the approximate chiral symmetry of the light-quark sector of QCD ("chiral perturbation theory").

Now having stable nuclei, the next level are atoms, understood very well using quantum electrodynamics. Then the atoms bind together to molecules and finally condensed matter, all of which is in principle also well described by QED, but it's QED for many-body systems, and there again one has models derivable from QED to effectively describe all kinds of properties of matter in terms of some constitutive relations (transport coefficients of various kinds like electric conductivity, viscosity, heat capacities and so on).

After all these levels of description you indeed end up with the known classical behavior of condensed matter systems, and among them are also the detectors used to measure quantum phenomena. From this phenomenological practical perspective there's no quibble concerning the validity of classical physics for macroscopic systems, including measurement devices.
 
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  • #6
lucas_ said:
Let us treat everything as quantum. Here are tables made up of atoms and electrons?
Basically yes they are and quantum field theory describes them very well. However in the usual approach to quantum theory you never treat everything as quantum at once, there's always some device involved treated classically.
 
  • #7
DarMM said:
Basically yes they are and quantum field theory describes them very well. However in the usual approach to quantum theory you never treat everything as quantum at once, there's always some device involved treated classically.

"TeethWhitener said: So does it even make sense to talk about a purely classical microscopic theory?

Atyy: "No, since we would like to say the classical measurement apparatus is made of electrons, which are quantum. However, quantum mechanics does not seem to allow us to say that."

Quantum mechanics does not seem to allow us to say what? How do you understand the puzzling passage above?
 
  • #8
lucas_ said:
Quantum mechanics does not seem to allow us to say what? How do you understand the puzzling passage above?
That some device is always rendered classical in the formalism and treated as if it was not made of atoms and particles.
 
  • #9
DarMM said:
Basically yes they are and quantum field theory describes them very well. However in the usual approach to quantum theory you never treat everything as quantum at once, there's always some device involved treated classically.

What would be the problem if you treat everything as quantum at once.. and neglect there is always some device involved treated classically?
 
  • #10
lucas_ said:
What would be the problem if you treat everything as quantum at once.. and neglect there is always some device involved treated classically?
The quantum formalism just refers to the probability ##P(E)## of some event/outcome ##E## being recorded in a classical device. The events ##E## don't refer to events that occur when no classical device is present.

Then if we describe a measuring device quantum mechanically we do so by a similar set of probabilities ##P(E)## but the events ##E## are outcomes recorded in another device treated classically.
 
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  • #11
DarMM said:
The quantum formalism just refers to the probability ##P(E)## of some event/outcome ##E## being recorded in a classical device. The events ##E## don't refer to events that occur when no classical device is present.

Then if we describe a measuring device quantum mechanically we do so by a similar set of probabilities ##P(E)## but the events ##E## are outcomes recorded in another device treated classically.

In other words, classical device is what produce eigenvalues of observables under the hermetian operators? Without classical device, there will never be any eigenvalues?

Without any humans let's say miles beneath venus. Why are there classical rock that produce eigenvalues in the position basis of example of the surrounding atoms?
 
  • #12
lucas_ said:
In other words, classical device is what produce eigenvalues of observables under the hermetian operators
Eigenvalues refer to possible values which might result in the classical device when it interacts with the microscopic system.

lucas_ said:
Without any humans let's say miles beneath venus.
Humans aren't necessary, just some system treated classically.
Why does it measure in a particular basis? Well if it's being treated classically simply because that is the type of device or system it is. A detection plate is set up to record localized marks for example.
If it's being treated quantum mechanically then the larger device would predict a strong correlation between features of the first device and the microscopic system in a particular basis due to decoherence.
 
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  • #13
DarMM said:
Basically when you use QM the device is treated in a special way by the formalism as purely classical "as if" it was not made of electrons and other quantum particles. Exactly why this is and the details of it are a bit subtle and a large part of Bohr's essays, so I'll only go into it if you wish.
lucas_ said:
What would be the problem if you treat everything as quantum at once.. and neglect there is always some device involved treated classically?

This is the point of view of Everett, of treating everything as quantum at once, and introducing a so-called "universal wave-function" Another reason people consider this idea is to address issues of the seemingly non-quantum behavior of large bodies, and how the “classical world arises out of quantum mechanics”

Bohr's central point related to this is that that you cannot have a "universal wavefunction." In any application of quantum theory, there must be some heavy objects which are placed "outside the description" so to speak, which define the situation and the possible phenomena that can appear. The classically described situation is specified by the classically defined parameters that enter into the Schrodinger differential equation. The fact that these measuring bodies can also be subjected to measurement only implies that there must be additional heavy bodies which must be introduced relative to which these measurements take place. There is no objective "classical" vs "quantum" cut, but in any application of the quantum mechanical formalism, there must be some bodies which are taken to be outside the description, without which the parameters entering into the schrodinger equation would not make any sense. The idea that quantum theory seems to apply to the “small” but not to the “large” is also based on a misunderstanding of the nature of the quantum formalism. There is indeed no such thing as quantum mechanics becoming invalid as the size or mass of the objects becomes large. It depends on the situation. In the double slit experiment, we can do two things. We can either use the diaphragm with the slits as a measuring body, and therefore outside the description, in which case we get interference. Or we can study the momentum exchange between the particle and the diaphragm, in which case we would be including the diaphragm on the "quantum side". In the latter case, there will be additional bodies introduced relative to which the momentum transferred to the diaphragm is controlled, and in that case we lose interference. So the diaphragm can either be a "classical" or a "quantum" object, depending on exactly what you are doing. The point however is that there must always be some bodies which are outside the description. Without those bodies, the parameters in the algebraic or differential equations of which the matrices or wave-functions are solutions are not defined.
 
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  • #14
PrashantGokaraju said:
This is the point of view of Everett, of treating everything as quantum at once, and introducing a so-called "universal wave-function" Another reason people consider this idea is to address issues of the seemingly non-quantum behavior of large bodies, and how the “classical world arises out of quantum mechanics”

So the detector in the double slit is the classical object that collapses the wave function of the electron. In Everett, it doesn't collapse it, but still is it not the detector as classical object is still there in Everett?
[/quote]Bohr's central point related to this is that that you cannot have a "universal wavefunction." In any application of quantum theory, there must be some heavy objects which are placed "outside the description" so to speak, which define the situation and the possible phenomena that can appear. The classically described situation is specified by the classically defined parameters that enter into the Schrodinger differential equation. The fact that these measuring bodies can also be subjected to measurement only implies that there must be additional heavy bodies which must be introduced relative to which these measurements take place. There is no objective "classical" vs "quantum" cut, but in any application of the quantum mechanical formalism, there must be some bodies which are taken to be outside the description, without which the parameters entering into the schrodinger equation would not make any sense. The idea that quantum theory seems to apply to the “small” but not to the “large” is also based on a misunderstanding of the nature of the quantum formalism. There is indeed no such thing as quantum mechanics becoming invalid as the size or mass of the objects becomes large. It depends on the situation. In the double slit experiment, we can do two things. We can either use the diaphragm with the slits as a measuring body, and therefore outside the description, in which case we get interference. Or we can study the momentum exchange between the particle and the diaphragm, in which case we would be including the diaphragm on the "quantum side". In the latter case, there will be additional bodies introduced relative to which the momentum transferred to the diaphragm is controlled, and in that case we lose interference. So the diaphragm can either be a "classical" or a "quantum" object, depending on exactly what you are doing. The point however is that there must always be some bodies which are outside the description. Without those bodies, the parameters in the algebraic or differential equations of which the matrices or wave-functions are solutions are not defined.
[/QUOTE]
 
  • #15
lucas_ said:
So the detector in the double slit is the classical object that collapses the wave function of the electron. In Everett, it doesn't collapse it, but still is it not the detector as classical object is still there in Everett?

In Everett, both the detector and electron are part of the wavefunction, i.e. both are "quantum objects" at the same time.
 
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  • #16
PrashantGokaraju said:
In Everett, both the detector and electron are part of the wavefunction, i.e. both are "quantum objects" at the same time.

So Bohr definition of classical is it collapses the wave function?

But note that in Everett, you still have classical in the sense that there is a built in preferred basis of position. Where does the position basis comes from? There is still classical bias.
 
  • #17
lucas_ said:
So Bohr definition of classical is it collapses the wave function?

The experimental arrangement would be the "classical" objects according to Bohr. As I said before, this does not mean that these same objects cannot be treated quantum mechanically. When they are treated like that, they are no longer part of the experimental arrangement, or they can no longer serve as measuring bodies. The capability of a clock to serve as a measuring device implies that the energy exchanged with it is uncontrollable. When such a control is attempted, it no longer can serve as a clock.

Also, the word "collapse" was never used by the founders of quantum mechanics. Certainly not by Bohr.
 
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  • #18
PrashantGokaraju said:
The experimental arrangement would be the "classical" objects according to Bohr. As I said before, this does not mean that these same objects cannot be treated quantum mechanically. When they are treated like that, they are no longer part of the experimental arrangement, or they can no longer serve as measuring bodies. The capability of a clock to serve as a measuring device implies that the energy exchanged with it is uncontrollable. When such a control is attempted, it no longer can serve as a clock.

Also, the word "collapse" was never used by the founders of quantum mechanics. Certainly not by Bohr.

I guess you are referring to the von Neumann chain?

Please elaborate what you mean by "The capability of a clock to serve as a measuring device implies that the energy exchanged with it is uncontrollable. When such a control is attempted, it no longer can serve as a clock.". What experiment in which a clock (grandpa's or digital clock?) was used as detector?
 
  • #19
By clock, i mean anything that can provide a time measurement. For example, a shutter for a slit, which leaves the slit open for a particular time. Using a shutter, you can say that the particle must have passed through the slit during the time the shutter was open.
 
  • #20
PrashantGokaraju said:
By clock, i mean anything that can provide a time measurement. For example, a shutter for a slit, which leaves the slit open for a particular time. Using a shutter, you can say that the particle must have passed through the slit during the time the shutter was open.

You were referring to this in the clock thing in the context of "Or we can study the momentum exchange between the particle and the diaphragm, in which case we would be including the diaphragm on the "quantum side". In the latter case, there will be additional bodies introduced relative to which the momentum transferred to the diaphragm is controlled, and in that case we lose interference."?
 
  • #21
The part of my post you quoted is about position measurements. For example, a rigid rod can be used to measure position, in which case the momentum exchanged with it is uncontrollable.

Say the shutter was velocity v, and the slit has a width dx. Then v dt = dx, where dt is the time the shutter is open. Hamilton's equation is v = dE/dp.

Substituting v = dE/dp in the first equation we get

(dE dt) / dp = dx

so

dE dt = dx dp

So using the position-momentum uncertainty principle dx dp ~ h, we get

dE dt ~ h

which is the time energy uncertainty principle.

A clock implies that the energy exchanged with it is uncontrollable. A measuring rod implies that the momentum exchanged with it is uncontrollable.
 
  • #22
lucas_ said:
So Bohr definition of classical is it collapses the wave function?
Bohr's definition of Classical is essentially a weaker form of "described by classical mechanics". Weaker in the sense that he didn't require a full Hamiltonian or Lagrangian description of its workings. Just that its properties form a classical event space/Boolean lattice. Although note in his essays Bohr conveys "Boolean lattice" by reference to essentially the "conditions of experience" Boole used as the motivation for his Boolean algebra.

Collapse was not viewed as a physical process by the Founders of QM as @PrashantGokaraju said. Rather when you observe event ##E## in the classical device you update the probabilities for future events. The quantum state was not viewed as a physical thing just a collection of probabilities ##P(E)## for events ##E##.
 
  • #23
DarMM said:
Bohr's definition of Classical is essentially a weaker form of "described by classical mechanics". Weaker in the sense that he didn't require a full Hamiltonian or Lagrangian description of its workings. Just that its properties form a classical event space/Boolean lattice. Although note in his essays Bohr conveys "Boolean lattice" by reference to essentially the "conditions of experience" Boole used as the motivation for his Boolean algebra.

Collapse was not viewed as a physical process by the Founders of QM as @PrashantGokaraju said. Rather when you observe event ##E## in the classical device you update the probabilities for future events. The quantum state was not viewed as a physical thing just a collection of probabilities ##P(E)## for events ##E##.

Who first used the word "collapse"?

But was it not Bohr proclaimed that "In the absence of measurement to determine the properties of a quantum particle like electron, the electron has no properties".

Is this not physical thing?
 
  • #24
I think it is von neumann who introduced the word "collapse".
 
  • #25
lucas_ said:
Who first used the word "collapse"?
I'm not sure. Heisenberg in his 1927 paper has the concept, but he emphaises it is not a physical process and doesn't use the word "collapse". Von Neumann did think of it as a physical "collapse" and I think like @PrashantGokaraju said he was the first to use the word.

lucas_ said:
But was it not Bohr proclaimed that "In the absence of measurement to determine the properties of a quantum particle like electron, the electron has no properties".

Is this not physical thing?
I'd need to see the precise quote.

However most likely Bohr is just saying that the quantum events ##E## refer to occurrences in a classical device due to the quantum system. QM does not speak of microscopic systems when there is no classical device around and thus tells us nothing about the system when such a device is absent. The only properties we can give to microscopic systems are their effects on a classical device. Remove the classical device and we have nothing to say.

This has nothing really to do with collapse.
 
  • #26
when I wrote this thread, I was confused by atyy statement that also got martinbn confused:

https://www.physicsforums.com/threads/is-quantum-theory-a-microscopic-theory.974961/page-2 msg 44

martinbn: That's not the issue. I am not talking about any measurements. @atyy said that QM doesn't allow (at least it seems so) to say that a classically behaving object is made out of quantum mechanical particles. My question is how so?

DarMM: I'm only assuming, so perhaps I'm wrong, my guess is that he was referring to the Von Neumann chain where one always has some system present that's not modeled as being made of quantum particles."

-------

I thought just like martinbn that atyy meant measuring apparatus didn't have to be composed of atoms or electrons.

atyy, did you still mean it somehow?

I want to explore the concept that object not to be composed of atoms or electrons.

This is because thermal agitations are supposed to be classical. In superconductivity, you have to lower the temperature of the wire so that the motions of the electrons would slow down and the cooper pairs would form. But if electrons were just illusions and a wire is composed of something else microscopically, then perhaps the thermal agitations is also illusion or something that can be turned off. This means the possibility of room temperature superconductor where the superconductivity can be induced not by lowering the temperature and inducing cooper pairs to form but directly influencing the substrate in other ways. This is the promise if objects were not really composed of atoms or electrons and these are just models for measurement purposes. Is this still possible? That our models of atoms and electrons were just for statistical purposes, and quantum theory is not really a microscopic theory as the other expert thread seems to suggest?
 
  • #27
lucas_ said:
I thought just like martinbn that atyy meant measuring apparatus didn't have to be composed of atoms or electrons
QM treats the classical device "as if" it were not made of atoms or electrons.

lucas_ said:
This is the promise if objects were not really composed of atoms or electrons and these are just models for measurement purposes. Is this still possible? That our models of atoms and electrons were just for statistical purposes, and quantum theory is not really a microscopic theory as the other expert thread seems to suggest?
Yes it is possible, but we have to very careful about what we mean.

So take a lump of material. Modern quantum field theory models this as a collection of events ##E##. Any given device you construct to examine the material is represented by a collection of such events ##\{E_{i}\}## that sum to the identity operator. The standard model gives us a precise recipe for what set of events are possible for a given piece of material, as well as rules for how the probabilities for those events ##P(E)## evolve in time.

Ultimately this set of events is vastly complex, but in certain limits the events will approximately decompose. I'm being very, very rough here to not make the post tedious, but take a cloud of hydrogen. We would find the set of events ##\mathcal{E}## for this cloud might approximately decompose as ##\mathcal{E} \approx \cup^N_i \mathcal{E}_i## with each ##\mathcal{E}_i## identical. We might then say that each event this cloud can cause in our devices can always be seen as a result of a particular collection of subevents. We then find that each subevent in a certain nonrelativistic limit decomposes as ##\mathcal{E}_i \approx \mathcal{E}_{i,e}\otimes\mathcal{E}_{i,p}##.

So every event behaves as if it were due to ##N## subevents and these subevents behave as if they were a pair of events. These final sets of events ##\mathcal{E}_{i,e}## and ##\mathcal{E}_{i,p}## have nice transformation properties that essentially show them to be the analogue in the quantum formalism of the classical concept of a "single relativistic object" and all these events have a well-defined charge.

Thus in a certain limit we can think of all the effects the cloud can cause in our device as being due to the cloud being composed of ##N## copies of a pair of objects with positive and negative charge, i.e. ##N## hydrogen atoms with each atom made of a proton and electron.

However we have to remember:
  1. The protons and electrons are only described in terms of statistics for events they cause in our devices. Not as things in and of themselves when no device is around. However the event algebra for the proton for example has all the mathematical properties required to render discussion of a single object as well defined so it causes no contradictions to think of these events being caused by "a single object"
  2. This decomposition is approximate. In general the set of events is too complex to permit it.
Ultimately the theory just describes the statistics of a enormous set of events/outcomes possible for a device (considered as classical) when it comes in contact with the cloud. In certain limits we recover the idea of the cloud being made of atoms as the event algebra tends to a collection of events each of which can be considered as due to a single object.
 
  • #28
lucas_ said:
I want to explore the concept that object not to be composed of atoms or electrons.

What concept, exactly, do you want to explore?

Suppose you wanted to make a rock starting from scratch. What would you use other than atoms or electrons?

Suppose you decided to take a rock apart into the smallest constituents you could obtain. What would you expect to obtain, other than atoms or electrons?

Don't confuse our scientific theories with the things those theories are about. The statements by @atyy that seem to be mystifying you are about our theories: quantum mechanics is a theory. When he says we have to treat some things classically in order to use QM, he's talking about a theory. His statements in no way imply that you could take apart a macroscopic object and get something other than atoms or electrons, nor that you could assemble a macroscopic object out of something other than atoms and electrons. All his statements are saying is that we humans don't currently have a theory that gives a complete understanding of how everything works.

lucas_ said:
Is this still possible?

No. See above.
 
  • #29
DarMM said:
QM treats the classical device "as if" it were not made of atoms or electrons.Yes it is possible, but we have to very careful about what we mean.

So take a lump of material. Modern quantum field theory models this as a collection of events ##E##. Any given device you construct to examine the material is represented by a collection of such events ##\{E_{i}\}## that sum to the identity operator. The standard model gives us a precise recipe for what set of events are possible for a given piece of material, as well as rules for how the probabilities for those events ##P(E)## evolve in time.

Ultimately this set of events is vastly complex, but in certain limits the events will approximately decompose. I'm being very, very rough here to not make the post tedious, but take a cloud of hydrogen. We would find the set of events ##\mathcal{E}## for this cloud might approximately decompose as ##\mathcal{E} \approx \cup^N_i \mathcal{E}_i## with each ##\mathcal{E}_i## identical. We might then say that each event this cloud can cause in our devices can always be seen as a result of a particular collection of subevents. We then find that each subevent in a certain nonrelativistic limit decomposes as ##\mathcal{E}_i \approx \mathcal{E}_{i,e}\otimes\mathcal{E}_{i,p}##.

So every event behaves as if it were due to ##N## subevents and these subevents behave as if they were a pair of events. These final sets of events ##\mathcal{E}_{i,e}## and ##\mathcal{E}_{i,p}## have nice transformation properties that essentially show them to be the analogue in the quantum formalism of the classical concept of a "single relativistic object" and all these events have a well-defined charge.

Thus in a certain limit we can think of all the effects the cloud can cause in our device as being due to the cloud being composed of ##N## copies of a pair of objects with positive and negative charge, i.e. ##N## hydrogen atoms with each atom made of a proton and electron.

However we have to remember:
  1. The protons and electrons are only described in terms of statistics for events they cause in our devices. Not as things in and of themselves when no device is around. However the event algebra for the proton for example has all the mathematical properties required to render discussion of a single object as well defined so it causes no contradictions to think of these events being caused by "a single object"
  2. This decomposition is approximate. In general the set of events is too complex to permit it.
Ultimately the theory just describes the statistics of a enormous set of events/outcomes possible for a device (considered as classical) when it comes in contact with the cloud. In certain limits we recover the idea of it being made of atoms as the event algebra tends to a collection of events each of which can be considered as due to a single object.

You haven't mentioned thermal or temperature. For you, there may be no way to initiate thermal override and recover molecular quantum coherence. But in principle it is possible? Please refer where in the description above you discussed the effect of thermal agitations. Thank you.
 
  • #30
lucas_ said:
You haven't mentioned thermal or temperature. For you, there may be no way to initiate thermal override and recover molecular quantum coherence. But in principle it is possible? Please refer where in the description above you discussed the effect of thermal agitations. Thank you.
The probabilities for the events can be ones corresponding to thermal states. Thermal effects are besides the point though.
 
  • #31
DarMM said:
The probabilities for the events can be ones corresponding to thermal states. Thermal effects are besides the point though.

Let's take the case of water molecules, H20. Conventionally, we know temperature makes the intermolecular bond forms and breaks and forms so fast at normal temperature..

Is there a way in principle to initiate more order in the intermolecular bonding still at normal temperature (based on your idea or descriptions above)? What extra hamiltonian (in principle) do you need to add in them to do this? (except freezing it or lowering the temperature)?
 
  • #32
lucas_ said:
Let's take the case of water molecules, H20. Conventionally, we know temperature makes the intermolecular bond forms and breaks and forms so fast at normal temperature..

Is there a way in principle to initiate more order in the intermolecular bonding still at normal temperature (based on your idea or descriptions above)? What extra hamiltonian (in principle) do you need to add in them to do this? (except freezing it or lowering the temperature)?
My descriptions above have nothing in particular to say about the thermal chemistry of water which will operate as chemists have found.

They concern two things.
  1. That quantum theory rather than directly describing microscopic systems is about describing them in terms of events ##E## representing effects on objects regarded as classical. The algebra of events is then much more general than that in classical mechanics.
  2. That a notion of matter being made of particles (this notion being represented as a certain decomposition of the event algebra) is only one recoverable in certain limits. Thankfully it's an approximation that is often valid.
 
  • #33
DarMM said:
My descriptions above have nothing in particular to say about the thermal chemistry of water which will operate as chemists have found.

They concern two things.
  1. That quantum theory rather than directly describing microscopic systems is about describing them in terms of events ##E## representing effects on objects regarded as classical. The algebra of events is then much more general than that in classical mechanics.
  2. That a notion of matter being made of particles (this notion being represented as a certain decomposition of the event algebra) is only one recoverable in certain limits. Thankfully it's an approximation that is often valid.

If I can show you that that it is possible to initiate some kind of ordering or coherency among individual water molecules without changing the temperature, or showing that it is possible to change the inter-molecular structure of liquid water. Is our QFT or QM still sufficient to describe it by perhaps adding extra hamiltonian of some kind? What must the Hamiltonian be to produce such effects in your descriptions a few messages back? This is the main question of this thread so please address this. Thanks.
 
  • #34
lucas_ said:
If I can show you that that it is possible to initiate some kind of ordering or coherency among individual water molecules without changing the temperature, or showing that it is possible to change the inter-molecular structure of liquid water. Is our QFT or QM still sufficient to describe it by perhaps adding extra hamiltonian of some kind? What must the Hamiltonian be to produce such effects in your descriptions a few messages back? This is the main question of this thread so please address this. Thanks.
My discussion in this thread is not about altering water in some hitherto unknown way. I have no posts about producing effects in water or what Hamiltonians might be needed to describe effects in water nobody as ever seen and I have little to say about such a topic.

The thread seemed to be about @atyy 's reference to the necessity of classical devices in QM, not new and untested ideas about hydrochemistry.
 
  • #35
DarMM said:
My discussion in this thread are not about altering water in some hitherto unknown way. I have no posts about producing effects in water or what Hamiltonians might be needed to describe effects in water nobody as ever seen and I have little to say about such a topic.

The thread seemed to be about @atyy 's reference to the necessity of classical devices in QM, not new and untested ideas about hydrochemistry.

Well. Let's say it's a good example.

We treat water or molecules are like marbles where brownian motions move them. But if they are all quantum objects, perhaps some global quantum effects can be recovered? This is especially if quantum mechanics is not theory of the microscopic as the other thread seems to suggest.
 

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