Angular Momentum, calculating uncertainties

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SUMMARY

The discussion focuses on calculating the uncertainties of angular momentum components Delta Lz and Delta Ly in quantum mechanics eigenstates |l,m> using raising and lowering operators. The user outlines the method to derive the uncertainties by expressing Lx and Ly in terms of the ladder operators L+ and L-. The key equations provided include (delta Lx)^2 = - ^2 and the definitions of Lx and Ly in terms of L+ and L-. The importance of operator order and orthogonality in quantum states is emphasized for accurate calculations.

PREREQUISITES
  • Understanding of quantum mechanics concepts, specifically angular momentum.
  • Familiarity with eigenstates and the notation |l,m>.
  • Knowledge of raising and lowering operators in quantum mechanics.
  • Basic proficiency in manipulating operators and calculating uncertainties.
NEXT STEPS
  • Study the derivation of the Heisenberg uncertainty principle in quantum mechanics.
  • Learn about the properties and applications of angular momentum operators in quantum systems.
  • Explore the mathematical techniques for calculating expectation values in quantum mechanics.
  • Review examples of using ladder operators in various quantum mechanical problems.
USEFUL FOR

Students and educators in quantum mechanics, physicists working with angular momentum, and anyone interested in mastering the application of raising and lowering operators in quantum calculations.

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Any help would be great! I'm just starting off with Quantum and am having trouble with this problem.

Homework Statement



Angular momentum eigenstates |l,m> satisfy the equality in the Heisenberg uncertainty relationship.

Calculate the uncertainties of Delta Lz and Delta Ly in an eigenstate |l,m> using raising and lowering operators.
 
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I'm never sure how to use latex code properly so I'll do my best to make everything as clear as possible.

The way to go about this, I'm pretty sure would be to write

(delta Lx)^2 = <Lx^2> - <Lx>^2

then express Lx in terms of the Ladder operators.

L+ = Lx + iLy

L- = Lx - iLy

so you get

Lx = ((L+) + (L-))/2

Ly = ((L+) - (L-))/2i

then you can substitute these into the first equation and perform the operations, keeping track of the order of operators, and using orthogonality to say that

<L1,m1|L2,m2> = (zero if L1 and m1 are not equal to L2 and M2 respectively) or 1 if they are equal.


hope that helps
 

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