Simple harmonic oscillators-Quantum mechanics

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SUMMARY

The discussion centers on the energy calculation of an ion in a harmonic ion trap, specifically after a measurement confirms it is in the n = 2 energy state. The energy formula used is E_n = (2n + 1)/2 ħω, where ħ represents the reduced Planck's constant and ω is the angular frequency, calculated as 2π times the frequency (1 MHz). The average energy for the nth state is clarified as E_n = (n + 1/2)ħω, providing a definitive understanding of energy levels in quantum harmonic oscillators.

PREREQUISITES
  • Understanding of quantum mechanics principles, particularly harmonic oscillators.
  • Familiarity with the concept of superposition in quantum states.
  • Knowledge of Planck's constant and its reduced form (ħ).
  • Basic grasp of angular frequency and its relationship to linear frequency.
NEXT STEPS
  • Study the derivation of the energy levels in quantum harmonic oscillators.
  • Learn about the implications of superposition in quantum mechanics.
  • Explore the mathematical formulation of angular frequency and its applications.
  • Investigate the role of Planck's constant in quantum mechanics and its significance in energy calculations.
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Students and professionals in physics, particularly those focusing on quantum mechanics and harmonic oscillators, as well as educators teaching these concepts.

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Homework Statement


An ion in a harmonic ion trap sees a potential which is effectively that of a simple harmonic
oscillator. It has a natural oscillation frequency given by v = 1 MHz. Ignoring any internal
excitations, it is known to be in a superposition of the n = 0, 1 and 2 SHO energy states.
A measurement is then made and it is found to be in the n = 2 level.

a)What is the energy of the ion after the measurement has been made?

The Attempt at a Solution


Why is the answer E_n = (2n+1)/2 \hbar\omega

I do not understand the (2n+1) / 2

Thanks!
 
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Hi,
The average energy in the nth state (or in the phonon picture: number of phonons in a mode associated with frequency \omega) for a single harmonic oscillator is given by:
E_n=\frac{2n+1}{2}\hbar\omega=(n+\frac{1}{2})\hbar\omega.
where
h\nu=\hbar\omega.
 

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