- #1
Jalo
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Homework Statement
Find the eigenvalues of the following Hamiltonian.
[itex]Ĥ = ħwâ^{†}â + \alpha(â + â^{†}) , \alpha \in |R[/itex]
Homework Equations
[itex]â|\phi_{n}>=\sqrt{n}|\phi_{n-1}>[/itex]
[itex]â^{†}|\phi_{n}>=\sqrt{n+1}|\phi_{n+1}>[/itex]
The Attempt at a Solution
By applying the Hamiltonian to a random state n I get:
[itex]Ĥ |\phi_{n}> = E_{n}|\phi_{n}>[/itex]
[itex]Ĥ |\phi_{n}>= ħwâ^{†}â|\phi_{n}> + \alpha(â|\phi_{n}> + â^{†}|\phi_{n}>) [/itex]
[itex]Ĥ |\phi_{n}>= ħw\sqrt{n}\sqrt{n}|\phi_{n}> + \alpha(\sqrt{n}|\phi_{n-1}> + \sqrt{n+1}|\phi_{n+1}> )[/itex]
[itex]E_{n} |\phi_{n}> = ħwn + \alpha(\sqrt{n}|\phi_{n-1}> + \sqrt{n+1}|\phi_{n+1}>) [/itex]
This is where my problem arrives. I don't know how to prove that
[itex]\alpha(\sqrt{n}|\phi_{n-1}> + \sqrt{n+1}|\phi_{n+1}>) = 0[/itex]
Any help would be highly appreciated!
Thanks.