Discussion
Electron pairs spin in opposing rotations, in agreement with the theory of conservation of angular momentum.
The spin of one of a pair can be changed using magnetic pulses.
When you then intercept the remaining electron (now a long way away in time and space from the flipped electron) to detect its spin rotation, it's always (so far) also flipped.
I may have the details incorrect, but the observation is consistent.
This clearly doesn't sit well with current models of time and space, not least because it requires the transmission of information faster than the speed of light.
Albert didn't like this result when the observation was first made during his lifetime (still missing you Albert).
So, we need to alter our model and come up with a more accurate one.
A bit like having to think of photons as existing in probability clouds instead of thinking of them as being hard particles or waves.
This is more consistent with the observation of what happens to some single photons (deflected) when they pass through a diffraction grating.
I've been out of the game for many years, so feel free to educate me as to where current thinking is at.
As Kamala would say ...... weird.
The spin of one of a pair can be changed using magnetic pulses.
When you then intercept the remaining electron (now a long way away in time and space from the flipped electron) to detect its spin rotation, it's always (so far) also flipped.
I may have the details incorrect, but the observation is consistent.
This clearly doesn't sit well with current models of time and space, not least because it requires the transmission of information faster than the speed of light.
Albert didn't like this result when the observation was first made during his lifetime (still missing you Albert).
So, we need to alter our model and come up with a more accurate one.
A bit like having to think of photons as existing in probability clouds instead of thinking of them as being hard particles or waves.
This is more consistent with the observation of what happens to some single photons (deflected) when they pass through a diffraction grating.
I've been out of the game for many years, so feel free to educate me as to where current thinking is at.
As Kamala would say ...... weird.
Edited by OIC on Sunday 13th April 17:45
Physicist here…but many years ago. So I’ll defer to Grok:
Entangled particles share a quantum state described by a single wavefunction. When you measure one particle, the wavefunction collapses, determining the state of both. This collapse is not a physical process traveling between particles but a change in our description of the system. No signal or energy moves faster than light.
Entangled particles share a quantum state described by a single wavefunction. When you measure one particle, the wavefunction collapses, determining the state of both. This collapse is not a physical process traveling between particles but a change in our description of the system. No signal or energy moves faster than light.
Read the wiki page on quantum entanglement, dig into it properly, and you'll see why you're wrong: https://en.wikipedia.org/wiki/Quantum_entanglement
Ultimately you're using a thought experiment on something which is only rigorously explained mathematically.
Ultimately you're using a thought experiment on something which is only rigorously explained mathematically.
nammynake said:
Physicist here…but many years ago. So I’ll defer to Grok:
Entangled particles share a quantum state described by a single wavefunction. When you measure one particle, the wavefunction collapses, determining the state of both. This collapse is not a physical process traveling between particles but a change in our description of the system. No signal or energy moves faster than light.
The "is it/isn't it a physical process" is debatable. What makes a measurement a measurement, what "collapse of the wave function" means in any physical sense ... these are not actually part of the maths of quantum mechanics, i.e. they are not really part of the formal model. The maths describes the time evolution of the wave function in a nice, deterministic way. How that relates to the observations we make ... err ... answers on a postcard, please, and a Nobel Prize may be dispatched on receipt.Entangled particles share a quantum state described by a single wavefunction. When you measure one particle, the wavefunction collapses, determining the state of both. This collapse is not a physical process traveling between particles but a change in our description of the system. No signal or energy moves faster than light.
geeks said:
Isn’t this what Einstein termed “a spooky action at a distance”?
Yes, in the context of "local" and "non-local" theories. "Local" roughly meaning that a thing can only be influenced by something else in close proximity to it.Classical physics is non-local. If you think about Newton's model of gravity, the Earth pulls on the Moon and vice versa, even though they are thousands of miles apart, and if you could magically shift the Earth 1000 miles to the left, the Moon would instantly be pulled towards the Earth's new location. That is also an example of the "spooky action at a distance" that Einstein objected to.
In Einstein's theory of gravity the presence of a mass bends the space where the mass is located and that bending propagates out through space and that propagation is not instantaneous. This is a local theory.
ATG said:
nammynake said:
Physicist here…but many years ago. So I’ll defer to Grok:
Entangled particles share a quantum state described by a single wavefunction. When you measure one particle, the wavefunction collapses, determining the state of both. This collapse is not a physical process traveling between particles but a change in our description of the system. No signal or energy moves faster than light.
The "is it/isn't it a physical process" is debatable. What makes a measurement a measurement, what "collapse of the wave function" means in any physical sense ... these are not actually part of the maths of quantum mechanics, i.e. they are not really part of the formal model. The maths describes the time evolution of the wave function in a nice, deterministic way. How that relates to the observations we make ... err ... answers on a postcard, please, and a Nobel Prize may be dispatched on receipt.Entangled particles share a quantum state described by a single wavefunction. When you measure one particle, the wavefunction collapses, determining the state of both. This collapse is not a physical process traveling between particles but a change in our description of the system. No signal or energy moves faster than light.
When I look out of my window, I see a countless array of particles. Whilst I am not observing individual particles or pairs of particles, I am observing them without being able to see them. If the theory is correct, then I'm constantly changing their behaviour.
(I did say that I'm a numpty)
RustyMX5 said:
Numpty here with a dumb comment
When I look out of my window, I see a countless array of particles. Whilst I am not observing individual particles or pairs of particles, I am observing them without being able to see them. If the theory is correct, then I'm constantly changing their behaviour.
(I did say that I'm a numpty)
Yes, if observation actually changes anythings behaviour, and that is a Big If, then by looking at things you are changing their behaviour. And that is bloody weird. When I look out of my window, I see a countless array of particles. Whilst I am not observing individual particles or pairs of particles, I am observing them without being able to see them. If the theory is correct, then I'm constantly changing their behaviour.
(I did say that I'm a numpty)
If you're interested, Google "the Copenhagen interpretation of quantum mechanics". I like it because it is unashamedly hopeless. It doesn't pretend there isn't a big gaping hole in the theory. It makes no attempt to explain what making a measurement means nor why the measuring equipment is "classical" while the thing it is measuring is "quantum". It doesn't literally say "there's this big thing called The Measurement Problem, and it beats the s
t out of us", but you don't have to read between the lines to see that that is the case.ATG said:
RustyMX5 said:
Numpty here with a dumb comment
When I look out of my window, I see a countless array of particles. Whilst I am not observing individual particles or pairs of particles, I am observing them without being able to see them. If the theory is correct, then I'm constantly changing their behaviour.
(I did say that I'm a numpty)
Yes, if observation actually changes anythings behaviour, and that is a Big If, then by looking at things you are changing their behaviour. And that is bloody weird. When I look out of my window, I see a countless array of particles. Whilst I am not observing individual particles or pairs of particles, I am observing them without being able to see them. If the theory is correct, then I'm constantly changing their behaviour.
(I did say that I'm a numpty)
If you look at the classical double slit experiment, which can be performed either with light or electrons, they will both give a wave-like interference pattern when observed. But if you actually measure which slit each particle passes through then the interference pattern disappears and they revert to particle-like arrays.
When you're looking out of your window, although you're observing a whole array of particles, you aren't seeing them with enough resolution to determine their precise state, and so aren't changing anything.
thegreenhell said:
ATG said:
RustyMX5 said:
Numpty here with a dumb comment
When I look out of my window, I see a countless array of particles. Whilst I am not observing individual particles or pairs of particles, I am observing them without being able to see them. If the theory is correct, then I'm constantly changing their behaviour.
(I did say that I'm a numpty)
Yes, if observation actually changes anythings behaviour, and that is a Big If, then by looking at things you are changing their behaviour. And that is bloody weird. When I look out of my window, I see a countless array of particles. Whilst I am not observing individual particles or pairs of particles, I am observing them without being able to see them. If the theory is correct, then I'm constantly changing their behaviour.
(I did say that I'm a numpty)
If you look at the classical double slit experiment, which can be performed either with light or electrons, they will both give a wave-like interference pattern when observed. But if you actually measure which slit each particle passes through then the interference pattern disappears and they revert to particle-like arrays.
When you're looking out of your window, although you're observing a whole array of particles, you aren't seeing them with enough resolution to determine their precise state, and so aren't changing anything.
thegreenhell said:
From my numpty understanding, it's the physical measurement of state rather than mere observation that changes behaviour of particles.
If you look at the classical double slit experiment, which can be performed either with light or electrons, they will both give a wave-like interference pattern when observed. But if you actually measure which slit each particle passes through then the interference pattern disappears and they revert to particle-like arrays.
When you're looking out of your window, although you're observing a whole array of particles, you aren't seeing them with enough resolution to determine their precise state, and so aren't changing anything.
Looking out the window is just as much a measurement as listening to a Geiger counter clicking away. If you look at the classical double slit experiment, which can be performed either with light or electrons, they will both give a wave-like interference pattern when observed. But if you actually measure which slit each particle passes through then the interference pattern disappears and they revert to particle-like arrays.
When you're looking out of your window, although you're observing a whole array of particles, you aren't seeing them with enough resolution to determine their precise state, and so aren't changing anything.
In the double slit experiment, if the particles' positions are measured as they enters the slits, what you actually get is single slit diffraction patterns from both slits that don't interfere with each other. You don't magically make them start behaving like classical particles. They are still quantum particles in a system which happens to make their Schroedinger waviness look like spatial waves.
It's dodgy to talk about the behaviour of the particle being changed by measurement. That's one possible interpretation that can be laid on top of QM, but as I said, there is nothing in the maths that describes anything like that process.
The Schroedinger equation describes the time-evolving probability disruption of the values we'll observe for some state of a quantum system when we measure it. That's it. There's no need to talk about "being in more than one state at the same time" nor to talk about "the collapse of the wave function". There's no need to think that the wave function is real. QM is a sausage machine that churns out predictions. Why it works, how it should be interpreted; those are open questions.
If you've got an entangled pair of particles, all you're saying is that the system compromised of the two particles has some conserved state. For example, the total angular momentum might be zero. If one particle has an angular momentum of X, then there other one must have a value of -X. Before we measure one of the particles' angular momentum, we only know the probability disruption of the values of X that will be seen if we make a measurement. So we measure one particle's angular momentum and discover it has the value +1/2. That tells us immediately that if we measured the other particle's angular momentum, we'd get a value of -1/2.
Gassing Station | Science! | Top of Page | What's New | My Stuff