Expectation of Position of a Harmonic Oscillator

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SUMMARY

The expectation value of the position operator for a Harmonic Oscillator is calculated using the raising and lowering operators. The position operator is defined as \(\hat{x}=\sqrt{\frac{\hbar}{2m\omega}}(a+a^{\dagger})\). The expectation value is expressed as \(\sqrt{\frac{\hbar}{2m\omega}}\), where only the \(a^{\dagger}\) operator contributes to the transition from the ground state \(|E_{0}>\) to the first excited state \(|E_{1}>\). The \(a\) operator does not contribute as it annihilates the ground state, confirming that the expectation value simplifies to \(\sqrt{\frac{\hbar}{2m\omega}}=\).

PREREQUISITES
  • Understanding of quantum mechanics principles, specifically Harmonic Oscillators.
  • Familiarity with raising and lowering operators in quantum mechanics.
  • Knowledge of expectation values in quantum states.
  • Basic understanding of Dirac notation and quantum state representations.
NEXT STEPS
  • Study the derivation of the position operator in quantum mechanics.
  • Learn about the properties and applications of raising and lowering operators.
  • Explore the concept of expectation values in various quantum systems.
  • Investigate the implications of the Harmonic Oscillator model in quantum field theory.
USEFUL FOR

Students and professionals in physics, particularly those focusing on quantum mechanics and harmonic oscillator models, as well as educators teaching these concepts.

Sekonda
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Hey,

My question is on determing the expectation value of position of the Harmonic Oscillator using raising and lowering operators, the question is part d) below:

Position.png


I have determined the position operator to be:

\hat{x}=\sqrt{\frac{\hbar}{2m\omega}}(a+a^{\dagger})

and so the expectation value becomes:

\sqrt{\frac{\hbar}{2m\omega}}<E_{1}|(a+a^{\dagger})|E_{0}>

Though this is the bit I'm not sure about, I think only the a-dagger operator acts to increase the E-zero ket and the 'a' operator just causes the state to go to zero thus:

\sqrt{\frac{\hbar}{2m\omega}}=<E_{1}|\hat{x}|E_{0}>

Can someone confirm this?

Cheers,
SK
 
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Looks good.
 

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