Quantum Mechanics: How Do I Find Expectation Values for Position and Momentum?

In summary, an expectation value problem is a mathematical problem used in quantum mechanics to find the average value of a physical quantity. The expectation value is calculated by taking the integral of the product of the wave function and the operator representing the physical quantity, and represents the most probable measurement result. The uncertainty principle places a limit on the precision of measuring certain physical quantities simultaneously, but their expectation values can still be calculated. Examples of expectation value problems include finding the average position, momentum, energy, spin, and angular momentum of particles or systems.
  • #1
itsaakanksha
1
0
Expectation value problem pleasezzz help ASAP

Hi Everyone,

I have a problem on one of my problems in the quantum course.

I need tofind the expectation values <x>,<x^2>, <p> & <p^2> for the function

e^(-(x-xo)^2/2k^2)

please email me if you need theformulaes..

i have them but i get stuck up doing the integration.

letme know
thanks,

Aakanksha Panjwani

ITS URGENT
 
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  • #2
Aakanksha, show us where you are stuck. Also, you have not mentioned what the bounds are : are they +infty to -infty ?
 
  • #3


Hi Aakanksha,

I understand your urgency to solve this expectation value problem. An expectation value problem in quantum mechanics deals with finding the average value of a physical quantity, such as position or momentum, in a given state. In your case, you are looking for the expectation values of position and momentum for the given function.

To solve this problem, you will need to use the formula for calculating expectation values: <A> = integral of A(x) * |ψ(x)|^2 dx, where A(x) is the physical quantity and ψ(x) is the wave function.

For <x>, you will need to use the formula A(x) = x and ψ(x) = e^(-(x-xo)^2/2k^2). This will give you the integral of xe^(-(x-xo)^2/2k^2) dx, which can be solved using methods of integration such as substitution or integration by parts.

Similarly, for <x^2>, you will need to use the formula A(x) = x^2 and for <p> and <p^2>, you will need to use the momentum operator, A(x) = -iħ(d/dx) and A(x) = (-iħ)^2(d^2/dx^2), respectively.

I hope this helps you solve the problem. If you are still stuck, I suggest reaching out to your professor or classmates for assistance. Good luck!
 

What is an expectation value problem?

An expectation value problem is a mathematical problem that involves finding the average value of a physical quantity in quantum mechanics. It is used to predict the outcome of a measurement and is an important concept in understanding the behavior of quantum systems.

How is the expectation value calculated?

The expectation value is calculated by taking the integral of the product of the wave function and the operator representing the physical quantity being measured. This integral is then divided by the total wave function squared.

What does the expectation value represent?

The expectation value represents the most probable measurement result for a given physical quantity. It is the average value that would be obtained if the measurement were repeated many times on identical systems.

How does the uncertainty principle relate to expectation values?

The uncertainty principle states that there is a fundamental limit to the precision with which certain pairs of physical quantities can be known simultaneously. The expectation value of these quantities can still be calculated, but their precise values cannot be determined at the same time.

What are some examples of expectation value problems?

Some examples of expectation value problems include finding the average position, momentum, or energy of a particle, as well as the average spin or angular momentum of a system. These problems are commonly encountered in quantum mechanics and help to understand the behavior of particles on a microscopic level.

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