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Lunct
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When measured/viewed particles in superposition collapse and take the form of one state. So how do we know they are in superposition in the first place. And do we know why they collapse into one state?
Lunct said:When measured/viewed particles in superposition collapse and take the form of one state. So how do we know they are in superposition in the first place. And do we know why they collapse into one state?
I'm sorry I did not understand that.PeroK said:This question is based on a fundamental misunderstanding of superposition. Every state is a single state and, at the same time, a superposition of other states.
Essentially a state is a vector and a vector, as you know, is a single vector and linear combination of other vectors.
Lunct said:I'm sorry I did not understand that.
So essentially the superposition only "collapses" after a specific measurement to the particle. Is that how it works?PeroK said:I would say it is one of the most common misconceptions about superposition. Also, "collapse" is a really misleading word, IMHO. In the Copenhagen interpretation, the state changes suddenly after a measurement to the relevant eigenstate of the observable.
This "collapsed" state is just as much a state as any other. In fact, in terms of position, say, the eigenstates are not
physically realisable, so after a position measurement the state "collapses" into a continuous distribution of position eigenstates - which is sometimes known as a "wave-packet". THis is just a regular state, albeit localised about a particular point.
It's analogous to the way that I can describe the position of something as "one kilometer to the north and one kilometer to the east" or as "1.414 kilometers northeast, zero kilometers northwest". The first description is more convenient if I'm looking at a map with north up and north/south and east/west gridlines on it; the second is more convenient if I'm in a city whose streets are laid out in a grid pattern with downtown/uptown avenes running from southwest to northeast and crosstown streets at right angles to the avenues. One way, my basis vectors are north/east, the other ways they're uptown/crosstown. But it's the same point with the same physical relationship to me either way.Lunct said:I'm sorry I did not understand that.
Lunct said:So essentially the superposition only "collapses" after a specific measurement to the particle. Is that how it works?
The Copenhagen interpretation says that we can never find out why it "collapses", right?PeroK said:That's the Copenhagen interpretation. There are other interpretations, but to get you started on QM Copenhagen is as good as any. So, yes, a measurements "collapses" the system into an eigenstate of the observable, with the eigenstate correspondiong to the eigenvalue returned by the measurement.
Lunct said:The Copenhagen interpretation says that we can never find out why it "collapses", right?
Thank youvanhees71 said:The Copenhagen Interpretation doesn't exist. There are many flavors of it, some with collapse, some without. IMHO QT is much less weird when avoiding collapse arguments. There are tons of arguments for and against this opinion in this forum. Just use the Search function.
Thank you as wellPeroK said:Yes, there's no why in that sense.
Lunct said:When measured/viewed particles in superposition collapse and take the form of one state. So how do we know they are in superposition in the first place.
However, here is a modification of your question which I think you may have intended (and if not, I'm pretty sure it will teach you something useful anyhow!).PeroK said:This question is based on a fundamental misunderstanding of superposition. Every state is a single state and, at the same time, a superposition of other states. Essentially a state is a vector and a vector, as you know, is a single vector and linear combination of other vectors.
Lunct said:And do we know why they collapse into one state?
Is that where the interpretations of QT come in, like the Many Words interpretation?Physics Footnotes said:Forgetting my quibbles about how you've phrased the question, the answer is, no we don't.
Superposition is a quantum physics principle that states that a particle can exist in multiple states or positions at the same time.
Superposition can be observed through experiments that involve measuring the properties of a particle, such as its position or momentum. These measurements can show that the particle exists in multiple states simultaneously.
There is a significant amount of experimental evidence from various fields of quantum physics, such as the double-slit experiment and the Stern-Gerlach experiment, that supports the existence of superposition. Additionally, many quantum mechanical theories and equations, such as the Schrödinger equation, rely on the principle of superposition to accurately describe the behavior of subatomic particles.
The principle of superposition has led to many groundbreaking discoveries in the field of quantum physics and has challenged our understanding of reality. It has also played a crucial role in the development of technologies such as quantum computing and cryptography.
No, superposition is only observed at the subatomic level and does not have any observable effects on larger objects in our everyday lives. However, certain technologies, such as transistors in computer processors, rely on the principles of superposition to function.