- #1
SchroedingersLion
- 215
- 57
Hello guys,
I am trying to understand the following experiment:
1. Prepare a 2 level atom in state |0>
2. Shine in a Pi/2 pulse --> atom goes to 1/√2 (|0>+|1>)
3. Wait time T
4. Shine in second Pi/2 pulse
a) if the state is pure: atom will go to state |1>, p1=1
b) if the state is mixed: p1=1/2, p2=1/2
And below a plot of p1 with respect to T. It starts at p1=1 and decreases with T to 1/2.
I don't understand point 4.
What I understand:
If T=0, the state is a pure superposition and gets to |1> via the second Pi/2 pulse
But as soon as time T passes after the first pulse, I am losing information, since the atom interacts with the vacuum fields (who are also responsible for spontaneous emission).
But what does that mean? Does the interaction with the vacuum 'destroy' my superposition and force the atom into either state |0> or state |1>?
Because if I then apply my second light pulse, it would go either from |0> to 1/√2 (|0>+|1>) or from |1> to 1/√2 (|0>+|1>), and then I would have my probabilities at 1/2.
Regards
I am trying to understand the following experiment:
1. Prepare a 2 level atom in state |0>
2. Shine in a Pi/2 pulse --> atom goes to 1/√2 (|0>+|1>)
3. Wait time T
4. Shine in second Pi/2 pulse
a) if the state is pure: atom will go to state |1>, p1=1
b) if the state is mixed: p1=1/2, p2=1/2
And below a plot of p1 with respect to T. It starts at p1=1 and decreases with T to 1/2.
I don't understand point 4.
What I understand:
If T=0, the state is a pure superposition and gets to |1> via the second Pi/2 pulse
But as soon as time T passes after the first pulse, I am losing information, since the atom interacts with the vacuum fields (who are also responsible for spontaneous emission).
But what does that mean? Does the interaction with the vacuum 'destroy' my superposition and force the atom into either state |0> or state |1>?
Because if I then apply my second light pulse, it would go either from |0> to 1/√2 (|0>+|1>) or from |1> to 1/√2 (|0>+|1>), and then I would have my probabilities at 1/2.
Regards