How Does Rotating the Local Basis Affect Quantum Entanglement of Photons?

  • Context: Graduate 
  • Thread starter Thread starter fulis
  • Start date Start date
  • Tags Tags
    Entanglement Photon
Click For Summary
SUMMARY

The discussion focuses on the effects of rotating the local basis on the quantum entanglement of photons. A user experimented with entangled photon states, initially using the state |1,V>|2,V> + |1,H>|2,H> and then modifying it to |1,V>|2,H> + |1,H>|2,V>. The user expected to derive a specific entangled state but encountered a contradiction in their calculations. The conversation highlights the importance of precise calculations in quantum mechanics and the need for clarity in quantum state representations.

PREREQUISITES
  • Understanding of quantum mechanics principles, particularly photon entanglement.
  • Familiarity with quantum state notation and superposition.
  • Knowledge of local basis rotation in quantum systems.
  • Basic skills in performing quantum state calculations.
NEXT STEPS
  • Study the mathematical framework of quantum entanglement in detail.
  • Learn about the implications of local basis rotation in quantum mechanics.
  • Explore the concept of normalization in quantum state calculations.
  • Investigate the differences between entangled and separable states in quantum systems.
USEFUL FOR

Quantum physicists, students of quantum mechanics, and researchers interested in the intricacies of photon entanglement and quantum state manipulation.

fulis
Messages
6
Reaction score
0
A question came up about entanglement and I've only studied very little QM so far, so I went to wikipedia to see if I could become any wiser and they had an example on photon entanglement which was quite straight forward (though the whole page lacks sources =[ ). The example shows that if you have photons going in opposite directions and that are entangled such that they will have the same polarization and their state is a superposition of vertical and horizontal polarization states then they actually don't have a polarization. Kind of a neat result.

Anyway, I figured I'd try to change the example a bit by having the two photons have opposite polarizations instead, so instead of the state:
|1,V>|2,V>+|1,H>|2,H>
I used:
|1,V>|2,H>+|1,H>|2,V>

I did the exact same substitution for the V and H states as they did in the example. I was expecting to get:
|1,45>|2,135>+|1,135>|2,45> since the photons are entangled in such a way that they have opposite polarization, but instead I got (I haven't normalized any of these expressions):
|1,45>|2,45>-|1,135>|2,135>

which is contradictory to the entanglement. The actual calculation is really simple and I did double check it a few times so I'm guessing the problem is something else. It's not exactly the best written wiki entry so I don't trust it to be right :D if someone else could show me how you actually calculate it I'd be grateful
 
Physics news on Phys.org
You'll have to be more precise... |1V>|2H> + |1H>|2V> seems to me like a perfectly formed quantum state of two photons (modulo normalization, of course). Why do you rotate the local basis?
 

Similar threads

  • · Replies 41 ·
2
Replies
41
Views
7K
  • · Replies 27 ·
Replies
27
Views
2K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 58 ·
2
Replies
58
Views
5K
  • · Replies 7 ·
Replies
7
Views
2K
Replies
13
Views
2K
  • · Replies 15 ·
Replies
15
Views
4K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 61 ·
3
Replies
61
Views
5K