Is My Quantum Mechanics Probability Calculation Correct?

In summary, the problem is asking to express the probability for simultaneous measurements of position and momentum in terms of the normalized wave function of a particle. The result obtained is an integral expression involving the wave function and the projectors for position and momentum. It is unclear if this is the simplest or most concrete answer.
  • #1
facenian
436
25

Homework Statement


Let [tex]\psi(x,y,z)=\psi(\vec{r})[/tex] be the normalized wave function of a particle.Express in terms of [itex]\psi(\vec{r})[/itex] the probability for a simultaneous measurements o X y P_z to yield :
[tex]x_1 \leq x \leq x_2[/tex]
[tex] p_z \geq 0[/tex]



Homework Equations


[tex]<\vec{p}|\vec{r}>=\frac{1}{(2\pi\hbar)^{3/2}}e^{-i\vec{p}.\vec{r}/\hbar} [/tex]
[tex]<\vec{p}|\psi>=\frac{1}{(2\pi\hbar)^{3/2}}\int \psi(\vec{r}) e^{-i\vec{p}.\vec{r}/\hbar} dr^3[/tex]


The Attempt at a Solution


I have reached the following result:
[tex]\int_{-\infty}^{\infty}dz\int_{-\infty}^{\infty}dy\int_{x_1}^{x_2}dx \int_{-\infty}^{\infty}dp_x\int_{-\infty}^{\infty}dp_y\int_0^{\infty}dp_z <\vec{p}|\vec{r}>\psi(\vec{r})<\psi|\vec{p}> [/tex]
I need to know two things: 1) is my result correct? 2) in case it is correct, is there any other more simple or concrete answer?
 
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  • #2
Sorry, I am not answering your question. But could you explain how you arrived at the expression [tex] <\vec{p}|\vec{r}>\psi(\vec{r})<\psi|\vec{p}>
[/tex]
 
  • #3
elduderino said:
Sorry, I am not answering your question. But could you explain how you arrived at the expression [tex] <\vec{p}|\vec{r}>\psi(\vec{r})<\psi|\vec{p}>
[/tex]

I evalueted de expression [itex]<\psi|P_2P_1|\psi>[/itex] where P_1 and P_2 are the proyectors:
[tex]P_1=\int_{-\infty}^{\infty}dz\int_{-\infty}^{\infty}dy\int_{x_1}^{x_2}dx|x,y,z><x,y,z|[/tex]
[tex]P_2=\int_{-\infty}^{\infty}dp_x\int_{-\infty}^{\infty}dp_y\int_0^{\infty}dp_z|p_x,p_y,p_z><p_x,p_y,p_z|[/tex]
But I'm sure whether what I'm doing is correct
 
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FAQ: Is My Quantum Mechanics Probability Calculation Correct?

1. What is the role of probabilities in quantum mechanics?

Probabilities play a crucial role in quantum mechanics as they describe the likelihood of a particular outcome or state of a system. In quantum mechanics, the state of a system is described by a wave function, and the square of the wave function gives the probability of finding the system in a particular state.

2. How is the probability of a quantum system calculated?

The probability of a quantum system is calculated using the Born rule, which states that the probability of finding a system in a particular state is equal to the square of the absolute value of the system's wave function at that state.

3. Can probabilities in quantum mechanics be predicted with certainty?

No, probabilities in quantum mechanics cannot be predicted with certainty. This is due to the inherent uncertainty principle in quantum mechanics, which states that it is impossible to know both the position and momentum of a particle with absolute certainty.

4. What is the difference between classical and quantum probabilities?

Classical probabilities are based on the idea of a deterministic universe, where the state of a system can be precisely determined. In contrast, quantum probabilities are based on the probabilistic nature of quantum systems and the uncertainty principle. Additionally, classical probabilities are continuous, while quantum probabilities are discrete and can only take on certain values.

5. How are probabilities used in practical applications of quantum mechanics?

Probabilities in quantum mechanics are used in practical applications such as quantum computing, cryptography, and quantum communication. These technologies rely on the manipulation and measurement of quantum states, which are described by probabilities. Additionally, probabilities are used in the interpretation of experimental results in quantum mechanics, allowing scientists to make predictions and test theories.

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