Question about superposition....

  • Context: Graduate 
  • Thread starter Thread starter Sundown444
  • Start date Start date
  • Tags Tags
    Superposition
Click For Summary

Discussion Overview

The discussion revolves around the concept of superposition in quantum mechanics, with participants seeking clarification and examples to aid understanding. The scope includes theoretical explanations, mathematical interpretations, and conceptual challenges related to both quantum mechanics and classical fields.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants express difficulty in understanding superposition and request real-life examples to clarify the concept.
  • One participant asserts that quantum mechanics does not have direct analogs in everyday life and quotes Richard Feynman on the complexity of the field.
  • There is a discussion about whether superposition applies only to subatomic particles or if it can also pertain to larger objects.
  • A participant explains that superposition can be understood mathematically through the decomposition of quantum states into basis states, likening it to vector resolution in classical physics.
  • Another participant introduces the double slit experiment as a practical example of superposition, highlighting how photons can interfere with themselves despite being emitted one at a time.
  • Some participants mention the Many Worlds Interpretation of quantum mechanics, discussing its relation to superposition and the concept of multiple outcomes existing in separate universes.
  • Schrödinger's cat is referenced as a thought experiment illustrating the challenges of conceptualizing superposition, particularly in relation to macroscopic objects.

Areas of Agreement / Disagreement

Participants express a range of views on the nature of superposition, with some seeking clarification while others provide technical explanations. There is no consensus on the applicability of superposition to macroscopic objects or the interpretation of quantum mechanics, indicating ongoing debate and uncertainty.

Contextual Notes

Participants' understanding of mathematics and physics varies, with some having limited exposure to quantum mechanics. The discussion includes assumptions about familiarity with concepts like vectors and linear algebra, which may not be universally shared.

Sundown444
Messages
179
Reaction score
7
Can anyone please describe to me how superposition in quantum mechanics works, preferably using real life places and objects as examples? I am having trouble understanding the concept.
 
Science news on Phys.org
Sorry but no. Quantum mechanics is not like anything in everyday life. You can learn how QM works by study, but :

It is safe to say that nobody understands quantum mechanics. Richard Feynman.
 
So it only applies to subatomic particles then, not objects?
 
Sundown444 said:
Can anyone please describe to me how superposition in quantum mechanics works,
Do you know how superposition works, mathematically, with classical fields, e.g. the electric field?
 
Sundown444 said:
Can anyone please describe to me how superposition in quantum mechanics works, preferably using real life places and objects as examples? I am having trouble understanding the concept.

What's your education, so far? What mathematics have you studied?
 
jtbell said:
Do you know how superposition works, mathematically, with classical fields, e.g. the electric field?

Not by much. Please tell me if you can.

Stephen Tashi said:
What's your education, so far? What mathematics have you studied?

I have Algebra and some Calculus, and I know a good amount of physics, though I haven't gone much into Quantum Mechanics yet. What I recall is that superposition is the idea that a system is in all possible states at the same time until it is observed.
 
Sundown444 said:
Not by much. Please tell me if you can.
I have Algebra and some Calculus, and I know a good amount of physics, though I haven't gone much into Quantum Mechanics yet. What I recall is that superposition is the idea that a system is in all possible states at the same time until it is observed.

If you know what a vector is, then you will be familiar with resolving a vector into the components in different directions.

For example, gravity near the surface of the Earth is a vertical vector. But, you can decompose that vector into, say, components tangential and normal to an inclined plane. And, in fact, you are free to decompose the vector into components in any pair of directions.

A quantum state is in fact an infinite dimensional vector. And superposition is the term used to describe its decomposition in a given basis of states.

Many people labour under the delusion that some states are in superposition and some are not. But, that is as absurd as saying some vectors can be decomposed and some cannot.

In short, given any state and any set of basis states, the state is in a superposition of those basis states. If you think, therefore, that superposition just means linear combination, then you'd be correct. Of course, if the basis you choose has the state in question as one of the basis states, then the superposition is trivial.

The role that linear algebra plays in QM goes much deeper than that. But, that's what a superposition is.
 
PeroK said:
If you know what a vector is, then you will be familiar with resolving a vector into the components in different directions.

For example, gravity near the surface of the Earth is a vertical vector. But, you can decompose that vector into, say, components tangential and normal to an inclined plane. And, in fact, you are free to decompose the vector into components in any pair of directions.

A quantum state is in fact an infinite dimensional vector. And superposition is the term used to describe its decomposition in a given basis of states.

Many people labour under the delusion that some states are in superposition and some are not. But, that is as absurd as saying some vectors can be decomposed and some cannot.

In short, given any state and any set of basis states, the state is in a superposition of those basis states. If you think, therefore, that superposition just means linear combination, then you'd be correct. Of course, if the basis you choose has the state in question as one of the basis states, then the superposition is trivial.

The role that linear algebra plays in QM goes much deeper than that. But, that's what a superposition is.

I see. Does it have anything to do with that many worlds theory thing?
 
Sundown444 said:
I see. Does it have anything to do with that many worlds theory thing?
I don't know much about the Many World's interpretation of QM. But, superposition is part of the core mathematical framework, so it's not specifically related to anyone interpretation.
 
  • #10
I think a good place to start is by looking at the double slit experiment. I hope you are familiar with this experiment.

The experiment with two slits proves that two light waves can interference constructively and deconstructively just like any wave. The interesting part of the experiment comes when you only shoot single photons at a time. Either photon can only go through one slit, so we shouldn't see a constructive or deconstructive pattern. How can a photon interfere with itself? Well, surprise surprise, it can interfere with itself. The photon is in a superposition of several states and these states can interact with each other.

If you are not aware of the experiment and what I am talking about, it would do you good to study the mathematical properties of waves and review a high school physics textbok.
 
Last edited:
  • #11
Sundown444 said:
Does it have anything to do with that many worlds theory thing?
The Many Worlds Interpretation in a nut shell gives each possible outcome its own "universe" to exist in, where the observed outcome relates to the universe we continue to exist in. Pilot wave theory simply gives a deterministic approach to the same probabilistic reality which is quantum superposition.
 
  • #12
Sundown444 said:
Can anyone please describe to me how superposition in quantum mechanics works
Schrödinger's cat is an example from way back, when QM was fairly new. Macroscopic objects don't behave this way but the thought experiment gives some clue as to why superposition is hard to conceptualize.
 

Similar threads

  • · Replies 23 ·
Replies
23
Views
10K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 5 ·
Replies
5
Views
4K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 124 ·
5
Replies
124
Views
9K