Is this a good understanding of superposition?

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Discussion Overview

The discussion revolves around the analogy of coin flipping as a representation of quantum superposition and entanglement. Participants explore whether this analogy accurately reflects the principles of superposition in quantum mechanics, comparing classical and quantum systems.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Exploratory

Main Points Raised

  • Some participants propose that flipping a coin and placing a hand over it illustrates superposition, suggesting the coin is in a state of both heads and tails until observed.
  • Others argue that using a coin is not a good analogy because it is a macroscopic object, and a quantum system like a qubit would be more appropriate.
  • A participant mentions that the analogy could be considered valid in the context of Bell states, referencing entangled states.
  • One participant highlights that classical analogies fail to capture key features of quantum mechanics, such as the behavior of entangled particles and the basis dependence of superposition.
  • Some participants assert that the analogy is fundamentally flawed, stating that the coin is definitely in one state when covered, thus not representing a true superposition.
  • Another participant emphasizes that there is no direct analogy for superposition or entanglement in the macroworld, suggesting that wave interference might be a limited model for superposition.
  • A participant discusses the distinctions between ordinary probability theory and quantum mechanics, noting that entanglement is a key factor that differentiates the two frameworks.

Areas of Agreement / Disagreement

Participants express a range of opinions on the validity of the coin analogy for superposition, with no consensus reached. Some find it a useful analogy, while others strongly disagree, indicating a significant divide in perspectives.

Contextual Notes

Participants note that classical analogies may not adequately represent the complexities of quantum phenomena, including the basis dependence of measurements and the unique characteristics of entangled states.

Addez123
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Say you flip a coin and place your hand above it before you view it.
Now the coin is in a super position where it's both heads and tails.
Once you look at it, you'll know what side is up and the wave function collapse.

Say you are flipping two coins instead. The odds of both being heads is 25%.
Both are hidden from you and thus are in a super position state of both heads and tails.
By viewing one of the coins you find out it's tails and therefore the odds of both being heads is 0%. You've successfully ruined both wave functions by simply viewing one coin. Welcome to entanglement.

Is this a proper analogy for super position?
 
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Addez123 said:
Say you flip a coin and place your hand above it before you view it.
Now the coin is in a super position where it's both heads and tails.

A coin is not a good example because it's a macroscopic object. You need to think of a quantum system with a two-dimensional Hilbert space, i.e,. a qubit.
 
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Addez123 said:
Say you flip a coin and place your hand above it before you view it.
Now the coin is in a super position where it's both heads and tails.
Once you look at it, you'll know what side is up and the wave function collapse.

Say you are flipping two coins instead. The odds of both being heads is 25%.
Both are hidden from you and thus are in a super position state of both heads and tails.
By viewing one of the coins you find out it's tails and therefore the odds of both being heads is 0%. You've successfully ruined both wave functions by simply viewing one coin. Welcome to entanglement.

Is this a proper analogy for super position?

Yes it is. It's called a Bell state.
https://en.wikipedia.org/wiki/Bell_state
 
As PeterDonis mentioned, there are several features of the quantum cases that do not easily carry over to the classical analogies.

One thing about two entangled coins is that separately they behave randomly, but together they're not. For example, if you have many pairs of entangle coins, then you could take one of each pair into one room and then flip them, and the other of the pairs into another room and also flip them. In each room the person flipping them will measure a completely random sequence of heads/tails but when they compared their sequence afterwards they will find that their random sequence was exactly identical (or exactly opposite depending on which entangled state they used). This feature is not captured by your classical analogy.

Also, for both superposition and entangled states, you need to remember that they are only in a superposition in a particular basis. If you take the same state, but measure in a different basis you can see an eigenstate. For example, the state |+> = |0> + |1> is a superposition in the 0/1 basis, meaning you measure randomly 0 or 1 every time, but if you measure in the +/- basis you get the same result every time. The randomness is basis dependent. This is also not captured in your classical analogy.
 
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Addez123 said:
Say you flip a coin and place your hand above it before you view it.
Now the coin is in a super position where it's both heads and tails.

Is this a proper analogy for super position?

No. When you have your hand over the coin, it is definitely heads or definitely tails. It is not a mixture.
 
Addez123 said:
Is this a proper analogy for super position?

No, this is a very bad analogy. Extremely bad. Actually, it is a perfect way to misunderstand quantum mechanics from the very beginning.

As for "entanglement", your analogy is also inappropriate.

Practically we do not have in a regular macroworld anything analogous to superposition or entanglement. Except may be for two waveves interference - that may somehow model (to some limited extent) what superposition is.
 
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MichPod said:
Practically we do not have in a regular macroworld anything analogous to superposition or entanglement. Except may be for two waveves interference - that may somehow model (to some limited extent) what superposition is.

Interestingly a critical analysis of the QM formalism shows entanglement is what separates ordinary probability theory and QM:
https://arxiv.org/abs/0911.0695

We know that the simplest generalized probability model is ordinary probability theory, but the next simplest is QM and two things separate them.

1. If you want continuous transformations between so called pure states then you must have QM.
2, If you want entanglement then you also need QM.

We understand the QM formalism a lot better these days than when it first came into being about 1925-1926 but what it means, or even if it meaning is an issue - :-p:-p:-p:-p:-p:-p:-p:-p

Thanks
Bill
 
A very long thread hijack that started with the claim that "I do not think that superposition, as I think you mean it, actually exists in the quantum world" has been removed from this thread.

A number of members had put a fair amount of work into thoughtful responses to that post; if you want a copy of your work please ask any of the mentors.
 
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