# Quantom physics Definition and 19 Discussions

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1. ### What do you think about "Neoclassical Theory of Electromagnetic Interactions" by Babin and Figotin?

TL;DR Summary: Book: Neoclassical Theory of Electromagnetic Interactions - A Single Theory for Macroscopic and Microscopic Scales I've found the book of Babin & Figotin: Neoclassical Theory of Electromagnetic Interactions - A Single Theory for Macroscopic and Microscopic Scales. I like their...
2. ### I Can someone explain why momentum does not commute with potential?

My assumption is that knowing potential can lead to knowing the position, but I don't know how this can be.
3. ### Landau Energy Spectrum in the non-relativistic limit

At non-relativistic limit, m>>p so let p=0 At non-relativistic limit m>>w, So factorise out m^2 from the square root to get: m*sqrt(1+2w(n+1/2)/m) Taylor expansion identity for sqrt(1+x) for small x gives: E=m+w(n+1/2) but it should equal E=p^2/2m +w(n+1/2), so how does m transform into p^2/2m?
4. ### I E=hf for massive particles, but which Energy exactly?

Hi there, I'm a bit confused about the E=hf equation for mass particle(f for frequency), and Lorentz Invariant (E^2 -p^2c^2=m^2c^4). The question is, which energy is it? Total Energy- Kinetic plus Rest, or only kinetic energy. Now, if it's total energy, then you get that a particle at rest...
5. ### I Difficulty in understanding step in Deriving WKB approximation

In Zettili book, it is given that ## \nabla^2 \psi \left( \vec{r} \right) + \dfrac{1}{\hbar ^2} p^2 \left( \vec{r} \right) \psi ( \vec{r} ) =0 ## where ## \hbar## is very small and ##p## is classical momentum. Now they assumed the ansatz that ## \psi ( \vec{r} ) = A ( \vec{r} ) e^{i S( \vec{r} )...
6. ### Show that an expected value of a vacuum state is equal to 1

\langle \phi_0| \hat{c}_{-k \downarrow} \hat{c}_{k \uparrow}\hat{c}^\dagger_{k \uparrow}\hat{c}_{-k \downarrow}|\phi_0\rangle = \\ \langle \phi_0| - \hat{c}_{k \uparrow} \hat{c}_{-k \downarrow} \hat{c}^\dagger_{k \uparrow}\hat{c}_{-k \downarrow}|\phi_0\rangle = \\ \langle \phi_0| \hat{c}_{k...
7. ### I Proving the Schrodinger Equation

How did scientists prove the accuracy of Schrodinger's equation to describe the behaviour of subatomic particles, especially in the 1920s? How do you monitor an electron's momentum and position when they are so small? Also, if the Schrodinger equation just describes probabilities, is the...
8. ### I Deduce if the spectrum is discrete/continuous from the potential

I have one-dimensional problem with a one-dimensional potential I want to know the energy domains that will result in discrete energy levels and the energy domains that will result in continuous energy levels In my lecture, my professor gave the example of v(r) = 1/r (r>0) (hydrogen atom...
9. ### I Problem with the idea of identical particles in QM

assume i have a gass made from N identical particles in a box and i want to calculate the probability for k out of N particles to be in the left side of the box. the problem is ,that if we treat the N particles as identical , each state in which exacly k of the N particles are in the left side...
10. ### I Pauli matrices

Hi :) I have several questions about the Pauli matrices, I have seen them when the lecturer showed us Stern-Gerlach experiment , and we did some really weird assumptions on what we think they should be. 1- why did we assume that all of those matrices should satisfy σ2 = I (the identity...
11. ### Particles with electric charges visible to the human eye?

Are there any particles known in the Physics world with an either positive or negative charge that can be viewed by the human eye under LED light illumination and have an attraction/repulsion to magnetism?
12. ### Hamiltonian of a 1D Linear Harmonic Oscillator

Homework Statement Show that for the one-dimensional linear harmonic oscillator the Hamiltonian is: [; H = \frac{1}{2}[P^2+\omega ^2 X^2]-\frac{1}{2}\omega \hbar ;] [; =\frac{1}{2}[P+i\omega X][P-i\omega X]+\frac{1}{2} \omega \hbar ;] where P, X are the momentum and position operators...
13. ### Qbit Questions

I am working on a project for our local science fair and decided on researching quantum computers. (This is what my focus will be in college.) Though, I expect to work on this far past the time allotted for that. I would like to build a superconductor based qubit using Josephson Junctions. The...
14. ### The relation between classical from quantum vs measurement perspective

What is the relation between classical from quantum vs measurement problem. On one hand they seem to be related on the other they seem to be of different nature. We always see our screens on front of us and not 100 meters away, that we say is classical object although the screen is a quantum...
15. ### Question about the Hamiltonian Operator

In my physical chemistry course, we are learning about the Schrödinger Equation and were introduced to the Hamiltonian Operator recently. We started out with the simple scenario of a particle in 1D space. Our professor's slide showed the following "derivation" to arrive at the expression for the...
16. ### What happens to the Hamiltonian of the wave function after measurement?

As I understand it, the Hamiltonian is the kinetic plus the potential energy of the wave function. When a measurement is done what happens to the kinetic and potential energy? Does it dissipate? Is it conserved in the measured state? Does it decrease? Does the Hamilton or kinetic+Potential...
17. ### Urgent, About the relationship of uncertainty principle and wave particle duality

Which of them comes first,(I mean the concept or the theory)? Did Heisenberg come up with the idea of uncertainty principle because of the discover of the wave particle duality? Thanks for paying attention~
18. ### Superposition and retrocausality

Hello guys, I made this analogy for double slit experiment. I would like to share this idea and I would like to hear your opinions and ideas. Thank you. I apologize for any typos or bad grammar, I am not native english speaker. Here it is: Analogy for wave collapse I am using term KNOWER...
19. ### Entangled Particles and the Hadron Collider?

If one was to entangle two particles and either send the two particles at each other, or send one of the entangled particles and observe the other; what do you think might happen? If there are any problems with getting an entangled particle into the Hadron Collider, please say so.