Creation and annihilation operators

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SUMMARY

The discussion focuses on the properties and relationships of creation and annihilation operators in quantum mechanics, specifically the equations a|n>=C|n-1> and a+|n>=D|n+1>. The annihilation operator (a) lowers the state of a ket vector, while the creation operator (a+) raises it. The normalization condition =1 is crucial for understanding the inner product relationships, leading to the conclusion that =C2. The confusion regarding the conjugation of operators is clarified, emphasizing that conjugation switches the order of expressions and transforms bras into kets and vice versa.

PREREQUISITES
  • Understanding of quantum mechanics terminology, specifically ket and bra notation.
  • Familiarity with linear algebra concepts, particularly inner products and normalization.
  • Knowledge of operator theory in quantum mechanics, including the roles of creation and annihilation operators.
  • Basic grasp of conjugation in mathematical expressions and its implications in quantum states.
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  • Study the mathematical derivation of the properties of creation and annihilation operators in quantum harmonic oscillators.
  • Learn about the implications of normalization in quantum state vectors and their physical interpretations.
  • Explore the role of conjugate operators in quantum mechanics and their effects on state transformations.
  • Investigate advanced topics in quantum mechanics, such as coherent states and their relationship with creation and annihilation operators.
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Students and professionals in quantum physics, particularly those studying quantum mechanics and operator theory. This discussion is beneficial for anyone seeking to deepen their understanding of the mathematical framework of quantum states and operators.

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- a|n>=C|n-1>
- a+|n>=D|n+1>

And because |n-1> is normalized, <n-1|n-1>=1: (<n|a+)(a|n>)=C2
Thus, <n|a+a|n>=C2

Where a is the annihilation operator and a+ is the creation operator

I don't understand this as isn't <n|a+=<n+1|D , thus <n|a+a|n> =<n+1|DC|n-1> instead?

This is from the quantum physics for dummies.
 
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No, the annihilation operator raises ket states, which it acts on from the left, but lowers bra states. The relation is simply the conjugation of a|n> = C|n-1>. Conjugation switches the order of the expressions, turn bras into kets, kets into bras, and conjugates operators.
 
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