Operator acting on ket state n

Glogower ladder operator, and it should act on a |n> state as follows:$$\left(\hat{N}+\mathbf{1}\right)^{-1 / 2} \alpha|n\rangle =\left(1-\frac{1}{2} \hat{N}+\frac{3}{8} \hat{N}^{2}-\cdots\right)\left(\sqrt{n}|n-1\rangle\right)=\frac{\sqrt{n}}{\sqrt{n-1}}|n-1\rangle$$In summary, the conversation is about how the operator (N+1)^-1/2 α acts on a |n> state of the harmonic oscillator,
  • #1
Jean-Mathys du bois
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TL;DR Summary
how does the operator (N+1)^-1/2 α act on a |n> state of harmonic osciliator? N is the number operator N|n>=n|n> and α anihilation operator
I tried playing with the number's operator eigenvalues equation but couldn't get anywhere, can s/b help me out?
 
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  • #2
If $$\hat{N}\left|n\right\rangle =n\left|n\right\rangle $$
then, by the very definition of function of operators, we have that
$$f(\hat{N})\left|n\right\rangle =f(n)\left|n\right\rangle $$
 
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Likes DrClaude and vanhees71
  • #3
Jean-Mathys du bois said:
Summary:: how does the operator (N+1)^-1/2 α act on a |n> state of harmonic osciliator? N is the number operator N|n>=n|n> and α anihilation operator

I tried playing with the number's operator eigenvalues equation but couldn't get anywhere, can s/b help me out?
To make sense of a non-polynomial function of an operator, you can interpret it as a Taylor series:
$$(1 + N)^{-1/2} = 1 - \frac 1 2 N + \frac 3 8 N^2 \dots $$
 
  • #4
The operator (N+1)^-1/2 α , i think is called Susskind
 

FAQ: Operator acting on ket state n

What is a ket state in quantum mechanics?

A ket state, denoted as |n⟩, is a vector in a complex Hilbert space that represents the state of a quantum system. It is part of the Dirac notation used in quantum mechanics, where kets are used to describe the state of particles, systems, or fields.

What does it mean for an operator to act on a ket state?

When an operator acts on a ket state, it transforms the state into another state, which can be either the same state or a different one. This operation is fundamental in quantum mechanics, as it allows us to calculate observable quantities and predict the behavior of quantum systems.

What are some common operators that act on ket states?

Common operators include the position operator (Ĥx), momentum operator (Ĥp), and Hamiltonian operator (ĤH). Each of these operators corresponds to a physical observable, and their action on ket states helps determine the properties of the quantum system being studied.

How do I calculate the result of an operator acting on a ket state?

To calculate the result, you apply the operator to the ket state using matrix multiplication if the states and operators are represented in a specific basis. The resulting state can be expressed as a linear combination of basis states, providing insights into the system's new state after the operation.

What is the significance of eigenstates and eigenvalues when an operator acts on a ket state?

Eigenstates are special ket states that remain unchanged, except for a scaling factor, when an operator acts on them. The corresponding scaling factor is called the eigenvalue. This relationship is crucial for understanding measurements in quantum mechanics, as measuring an observable associated with an operator will yield one of its eigenvalues, with the system collapsing into the corresponding eigenstate.

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