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**1. The problem statement**

I want to write the angular momentum operator ##L## for a 2-dimensional harmonic oscillator, in terms of its ladder operators, ##a_x##, ##a_y##, ##a_x^\dagger## & ##a_y^\dagger##, and then prove that this commutes with its Hamiltonian.

## The Attempt at a Solution

I get

##L = (x + y) × (p_x + p_y) = -i \hbar ((a_x^\dagger +a_y^\dagger) × (a_x + a_y) + a_x × a_x + a_y × a_y)##.

Does this seem to make any sense?

As for the commutator, with Hamiltonian ##H = \hbar \omega (a_x^\dagger a_x + a_y^\dagger a_y + 1) ##, I consequently get all sorts of exotic product terms, e.g.

## \left ( (a_x^\dagger +a_y^\dagger) × (a_x + a_y) \right ) a_x^\dagger a_x ##

and the like, and I'm not comfortable with handling these. I want all of them to go away, for said operators to commute, but am not sure how to do/see that.

Any comments would be appreciated.