Trying to learn the uncertainty principle

In summary: Planck's constant.In summary, the uncertainty principle is about the minimum amount of discrepancy between measurements of position and momentum. This discrepancy has a constant minimum, which is related to the Planck's constant.
  • #1
mjc456
4
0
I am trying to really, truly understand the uncertainty principle. I have done a lot of reading and self-study and listening to lectures online. I feel I'm getting closer, but would appreciate some help in directing my further efforts. Here is my horrible patchwork understanding thus far, which is no doubt riddled with misunderstandings and inaccuracies:
At some point we start calling measurements "operators". (The exact reason/justification for this, I'm not sure of). Like the "momentum" operator is what you use to calculate momentum. We start with a particle's wave function, which (I think) represents the probability distribution of the energy of the particle. For some reason real numbers aren't sufficient for this job, so complex numbers are involved in this (not sure why, and would like to find out). Anyway, we have this wave function, we apply an operator, say the "momentum operator", which is just a mathematical expression that we work on the whole wave function, and this transforms our old energy wave function into a new wave, which is also a complex function. This new wave maps the probability distribution of certain momentums.

The thing is that the "position" operator and the "momentum" operator don't commute, which means, the answers you get change when you reverse the order. This is much like matrix multiplication, in which (given matrices A and B) AB is not equal to BA. In fact, sure enough, it seems there are a bunch of linear algebra terms all through QM, but for QM what exactly there is that is supposed to comprise the elements of those matrices, I don't know. What do the matrices and their elements represent? How are they related to operators? And why do I need a Hilbert space?

The minimum amount of discrepancy between going Position then Momentum vs. Momentum then Position seems to be related to Planck's constant, and since the discrepancy has a constant minimum, voila, uncertainty principle.
Ok. So that was it. I would appreciate any help, either in the form of direct explanation, or even just some useful hyperlinks or books that I can read myself which would definitely address these issues. I'm not afraid to do the work myself, but I'm afraid I'll drown in information overload trying to just continue brute-force googling my way through the whole thing. Thanks for any consideration.

Also, I hope I posted this in the correct forum, if not I apologize and please let me know.
 
Last edited:
Physics news on Phys.org
  • #2
Hi.
The post seemed to me that you surely have eagerness to study QM.
I would like to recommend you one of may favorite books of a classic work of QM
https://www.amazon.com/dp/0198520115/?tag=pfamazon01-20
I was surprised to see there such expensive price. You may need some courage to purchase but it surely pays back. I hope you too like it.
Regards.
 
Last edited by a moderator:
  • #3
mjc456 said:
At some point we start calling measurements "operators". (The exact reason/justification for this, I'm not sure of).
I would say that it is the point where you move from real space into Hilbert space and represent ensemble using state vectors.

mjc456 said:
We start with a particle's wave function, which (I think) represents the probability distribution of the energy of the particle. For some reason real numbers aren't sufficient for this job, so complex numbers are involved in this (not sure why, and would like to find out).
It might be useful to look at http://en.wikipedia.org/wiki/Fourier_transform" . I guess it's because you don't have "real" (or do not have at all) time dimension when moving to Hilbert space.

mjc456 said:
Anyway, we have this wave function, we apply an operator, say the "momentum operator", which is just a mathematical expression that we work on the whole wave function, and this transforms our old energy wave function into a new wave, which is also a complex function. This new wave maps the probability distribution of certain momentums.

The thing is that the "position" operator and the "momentum" operator don't commute, which means, the answers you get change when you reverse the order. This is much like matrix multiplication, in which (given matrices A and B) AB is not equal to BA. In fact, sure enough, it seems there is a bunch of linear algebra terms all through QM, but for QM what exactly there is that is supposed to comprise the elements of those matrices, I don't know. What do the matrices and their elements represent? How are they related to operators? And why do I need a Hilbert space?

The minimum amount of discrepancy between going Position then Momentum vs. Momentum then Position seems to be related to Planck's constant, and since the discrepancy has a constant minimum, voila, uncertainty principle.
Have not come across nice experiments demonstrating Position/Momentum uncertainty. So I am hesitant to comment about that.
It's easier to think of experiments demonstrating uncertainty in polarization or spin measurements.
 
Last edited by a moderator:

FAQ: Trying to learn the uncertainty principle

What is the uncertainty principle?

The uncertainty principle, also known as the Heisenberg uncertainty principle, is a fundamental principle in quantum mechanics that states that it is impossible to know both the precise position and momentum of a particle at the same time.

Who discovered the uncertainty principle?

The uncertainty principle was first proposed by German physicist Werner Heisenberg in 1927.

Why is the uncertainty principle important?

The uncertainty principle is important because it sets limitations on our ability to measure and predict the behavior of particles at the quantum level. It also helps explain the wave-like behavior of particles and the probabilistic nature of quantum mechanics.

How does the uncertainty principle affect everyday life?

The uncertainty principle has very little impact on everyday life as it mainly applies to particles at the quantum level. However, it does play a crucial role in technologies such as transistors and computer chips, which rely on the behavior of particles at the quantum level.

Is the uncertainty principle proven?

Yes, the uncertainty principle has been extensively tested and confirmed through various experiments, including the famous double-slit experiment. It is a fundamental principle in quantum mechanics and is widely accepted by the scientific community.

Similar threads

Replies
3
Views
1K
Replies
17
Views
2K
Replies
12
Views
1K
Replies
8
Views
2K
Replies
10
Views
2K
Back
Top