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Bapelsin
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Show that wave packet is an eigenstate to operator [SOLVED]
For a harmonic oscillator we can define the step up and down operators [tex]\hat{a}[/tex] and [tex]\hat{a}^{\dagger}[/tex] and their action as
[tex]\hat{a}=\sqrt{\frac{m\omega}{2\hbar}}(\hat{x}+\frac{\imath}{m\omega}\hat{p}) \quad \hat{a}|n\rangle = \sqrt{n}|n-1\rangle[/tex]
[tex]\hat{a}^{\dagger}=\sqrt{\frac{m\omega}{2\hbar}}(\hat{x}-\frac{\imath}{m\omega}\hat{p}) \quad \hat{a}^{\dagger}|n\rangle = \sqrt{n+1}|n+1\rangle[/tex]
Show that the Gaussian wave-packet
[tex]\Psi(x)=\left(\frac{m\omega}{\pi\hbar}\right)^{1/4}e^{-\frac{m\omega}{2\hbar}(x-x_t)^2+\frac{\imath}{\hbar}p_t(x-x_t)}[/tex]
is an eigenstate to [tex]\hat{a}[/tex] with eigenvalue [tex]\alpha[/tex].
[tex]\hat{a}|a\rangle = \alpha | a\rangle[/tex]
Express the eigenvalue in terms of [tex]x_t[/tex] and [tex]p_t[/tex].
See above.
[tex]\hat{p} \rightarrow -i\hbar\frac{\partial}{\partial x}[/tex]
gives the expression for
[tex]\hat{a}=\sqrt{\frac{m\omega}{2\hbar}}(\hat{x}+\frac{\hbar}{m\omega}\frac{\partial}{\partial x})[/tex]
[tex]\hat{a}|\Psi\rangle = \sqrt{\frac{m\omega}{2\hbar}} \left(\frac{m\omega}{\pi\hbar}\right)^{1/4}\left(e^{-\frac{m\omega}{2\hbar}(x-x_t)^2+\frac{\imath}{\hbar}p_t(x-x_t)} + \frac{\hbar}{m\omega}(-\frac{m\omega}{\hbar}(x-x_t)+\frac{\imath}{\hbar}p_t(e^{-\frac{m\omega}{2\hbar}(x-x_t)^2+\frac{\imath}{\hbar}p_t(x-x_t)})\right) =
\Psi\sqrt{\frac{m\omega}{2\hbar}}\left(1+(x-x_t)+\frac{\imath}{m\omega}p_t\right)[/tex]
which is obviously not a scalar times [tex]\Psi[/tex].
What am I doing wrong here?
Homework Statement
For a harmonic oscillator we can define the step up and down operators [tex]\hat{a}[/tex] and [tex]\hat{a}^{\dagger}[/tex] and their action as
[tex]\hat{a}=\sqrt{\frac{m\omega}{2\hbar}}(\hat{x}+\frac{\imath}{m\omega}\hat{p}) \quad \hat{a}|n\rangle = \sqrt{n}|n-1\rangle[/tex]
[tex]\hat{a}^{\dagger}=\sqrt{\frac{m\omega}{2\hbar}}(\hat{x}-\frac{\imath}{m\omega}\hat{p}) \quad \hat{a}^{\dagger}|n\rangle = \sqrt{n+1}|n+1\rangle[/tex]
Show that the Gaussian wave-packet
[tex]\Psi(x)=\left(\frac{m\omega}{\pi\hbar}\right)^{1/4}e^{-\frac{m\omega}{2\hbar}(x-x_t)^2+\frac{\imath}{\hbar}p_t(x-x_t)}[/tex]
is an eigenstate to [tex]\hat{a}[/tex] with eigenvalue [tex]\alpha[/tex].
[tex]\hat{a}|a\rangle = \alpha | a\rangle[/tex]
Express the eigenvalue in terms of [tex]x_t[/tex] and [tex]p_t[/tex].
Homework Equations
See above.
The Attempt at a Solution
[tex]\hat{p} \rightarrow -i\hbar\frac{\partial}{\partial x}[/tex]
gives the expression for
[tex]\hat{a}=\sqrt{\frac{m\omega}{2\hbar}}(\hat{x}+\frac{\hbar}{m\omega}\frac{\partial}{\partial x})[/tex]
[tex]\hat{a}|\Psi\rangle = \sqrt{\frac{m\omega}{2\hbar}} \left(\frac{m\omega}{\pi\hbar}\right)^{1/4}\left(e^{-\frac{m\omega}{2\hbar}(x-x_t)^2+\frac{\imath}{\hbar}p_t(x-x_t)} + \frac{\hbar}{m\omega}(-\frac{m\omega}{\hbar}(x-x_t)+\frac{\imath}{\hbar}p_t(e^{-\frac{m\omega}{2\hbar}(x-x_t)^2+\frac{\imath}{\hbar}p_t(x-x_t)})\right) =
\Psi\sqrt{\frac{m\omega}{2\hbar}}\left(1+(x-x_t)+\frac{\imath}{m\omega}p_t\right)[/tex]
which is obviously not a scalar times [tex]\Psi[/tex].
What am I doing wrong here?
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