Quantum Mechanics: Coupled Electric Harmonic Oscillators

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SUMMARY

The discussion focuses on analyzing the quantum mechanics of coupled electric harmonic oscillators as described in Herbert Fröhlich's "Biological Coherence and Response to External Stimuli." The equations of motion for the system are given by \(\ddot{q_1}+\omega_{1}^2 q_{1}=-\gamma q_{2}\) and \(\ddot{q_2}+\omega_{2}^2 q_{2}=-\gamma q_{1}\), with the Hamiltonian defined as \(H=\frac{1}{2}(\dot{q_1}^2+\omega_{1}^2 q_{1}^2)+\frac{1}{2}(\dot{q_2}^2+\omega_{2}^2 q_{2}^2)+\gamma q_{1}q_{2}\). The primary challenge discussed is whether the Hamiltonian can be substituted into Schrödinger's Equation, given that the variables \(q_{1}\) and \(q_{2}\) represent position coordinates rather than charges. The solution involves finding the normal modes of oscillation to decouple the equations before quantizing them as harmonic oscillators.

PREREQUISITES
  • Understanding of quantum mechanics principles, specifically Schrödinger's Equation.
  • Familiarity with classical mechanics, particularly harmonic oscillators.
  • Knowledge of Hamiltonian mechanics and canonical coordinates.
  • Concept of normal modes in coupled oscillatory systems.
NEXT STEPS
  • Study the derivation and implications of Schrödinger's Equation in quantum mechanics.
  • Learn about normal mode analysis in coupled oscillators.
  • Explore Hamiltonian mechanics and its applications in quantum systems.
  • Investigate the quantization of harmonic oscillators and their significance in quantum field theory.
USEFUL FOR

Students and researchers in physics, particularly those focusing on quantum mechanics, coupled systems, and harmonic oscillators. This discussion is beneficial for anyone looking to deepen their understanding of quantum interactions in physical systems.

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Hi

I am doing this completely out of self interest and it is not my homework to do this.
I hope somebody can help me.

Homework Statement


In the book Biological Coherence and Response to External Stimuli Herbert Fröhlich wrote a chapter on Resonance Interaction. Where he considers the interaction of two electric harmonic oscillations with frequencies \omega_{1} and \omega_{2}at a distance R with a coupling constant \gamma which is proportional to \frac{1}{R^{3}}.
I want to analyze this system quantum mechanically.


Homework Equations



The equations of motions are

\ddot{q_1}+\omega_{1}^2 q_{1}=-\gamma q_{2}

\ddot{q_2}+\omega_{1}^2 q_{2}=-\gamma q_{1}

The Hamiltonian is given by

H=\frac{1}{2}(\dot{q_1}^2+\omega_{1}^2 q_{1}^2)+\frac{1}{2}(\dot{q_2}^2+\omega_{2}^2 q_{2}^2)+\gamma q_{1}q_{2}

The Attempt at a Solution



For a start we know Schrödinger's Equation:

i \overline{h} \frac{\partial \Psi}{\partial t}=H\Psi

My problem is: Can I substitute the Hamiltonian into Schrödingers Equation?
Because q1 and q2 are charges, aren't they?
 
Physics news on Phys.org
The variables ##q_{1}## and ##q_{2}## are not charges, they are position coordinates of particles. The hamiltonian should be a function of canonical momenta ##p_{i}=\frac{\partial L}{\partial \overset{.}{q}_{i}}## and position coordinates ##q_{i}##, not a function of ##\overset{.}{q}_{i}## and ##q_{i}##. In this case, however it does not matter because here ##p_{i} = \overset{.}{q}_{i}##.

To solve the problem, you first find the normal modes of the oscillation. You don't need any reference to quantum mechanics to do this. Then when you know the normal modes and can decouple the equations, you can quantize the modes as harmonic oscillators, changing classical position and momentum variables to corresponding operators.
 

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