Expectation of Position of a Harmonic Oscillator

Click For Summary
The discussion focuses on calculating the expectation value of position for a Harmonic Oscillator using 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 \(\sqrt{\frac{\hbar}{2m\omega}}<E_{1}|(a+a^{\dagger})|E_{0}>\). It is noted that only the raising operator \(a^{\dagger}\) contributes to increasing the energy state, while the lowering operator \(a\) results in the state going to zero. The conclusion confirms that the expectation value simplifies to \(\sqrt{\frac{\hbar}{2m\omega}}=<E_{1}|\hat{x}|E_{0}>\).
Sekonda
Messages
201
Reaction score
0
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}}&lt;E_{1}|(a+a^{\dagger})|E_{0}&gt;

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}}=&lt;E_{1}|\hat{x}|E_{0}&gt;

Can someone confirm this?

Cheers,
SK
 
Physics news on Phys.org
Looks good.
 
(a) The polarisation pattern is elliptical with maximum (1,1) and minimum (-1,-1), and anticlockwise in direction. (b) I know the solution is a quarter-wave plate oriented π/4, and half-wave plate at π/16, but don't understand how to reach there. I've obtained the polarisation vector (cos π/8, isin π/8) so far. I can't find much online guidance or textbook material working through this topic, so I'd appreciate any help I can get. Also, if anyone could let me know where I can get more...

Similar threads

  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 16 ·
Replies
16
Views
2K
Replies
11
Views
2K
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 1 ·
Replies
1
Views
3K
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K