I Transition probability and superposition

amjad-sh
Messages
240
Reaction score
13
Hello
suppose that we are dealing with a particle moving in an infinite potential well(a box of length L).
Let the wavefunction of the particle be \psi(x,t)=c1\psi_{1}(x,t)+...+cn\psi_{n}(x,t)
suppose that after measurement we find the particle at the energy eigenstate \psi_{1}(x,t).
Now let's change the size of the box to 2L. Let's find the probability of the particle being in state \phi_{1}(x) which is the ground state of the new box.The answer is |\int\phi^{*}_{1}(x)\psi_{1}(x)dx|^{2},which may in many cases be not equal to zero.
My confusion is here: what if we didn't change the box and we computed the same integral above, which is the probability of the particle to be in state \phi_{1}(x) and it is a non allowed state, the probability of course will not be zero because it is the same integral above.
How the probability of the particle in being in a non allowed state can be not equal to zero ?
 
Physics news on Phys.org
It's not the same integral as the limits are different.
 
Jilang said:
It's not the same integral as the limits are different.
No it is the same since \psi_{1}(x)=0 for x outside the interval [0,L].
 
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. Towards the end of the first lecture for the Qiskit Global Summer School 2025, Foundations of Quantum Mechanics, Olivia Lanes (Global Lead, Content and Education IBM) stated... Source: https://www.physicsforums.com/insights/quantum-entanglement-is-a-kinematic-fact-not-a-dynamical-effect/ by @RUTA
If we release an electron around a positively charged sphere, the initial state of electron is a linear combination of Hydrogen-like states. According to quantum mechanics, evolution of time would not change this initial state because the potential is time independent. However, classically we expect the electron to collide with the sphere. So, it seems that the quantum and classics predict different behaviours!

Similar threads

Replies
27
Views
2K
Replies
5
Views
1K
Replies
8
Views
1K
Replies
5
Views
1K
Replies
23
Views
1K
Replies
3
Views
1K
Back
Top