How Do Coherence and Entanglement Affect Photon Interference?

In summary: You can split it in different ways, but not in a uniquely defined way. You can use entanglement to learn more about the situation, but that does not mean that "the parts were entangled".In summary, The conversation discusses coherence and entanglement, specifically in relation to photon interference. It raises questions about the interference of incoherent photons, the increase of coherence when passing through a pin hole, and the relationship between coherence and brightness. It also questions the possibility of changing coherence and entanglement within the same photon or set of entangled photons. Finally, it considers the assumptions about entanglement between wave-functions passing through each slit in a single particle, double-slit experiment.
  • #1
San K
911
1
Trying to understand coherence and entanglement and have some questions:

1. Do incoherent photons interfere?
a) Single particle interference through double slit
b) Multiple photons through double slit
Is it that the interference pattern in the above cases is not a clear fringe pattern however there is still interference?
2. Why does coherence increase when light is passed through a pin hole?
3. Why does brighter light have higher coherence?
4. What does coherence within a single photon mean?
5. Can coherence be changed (is it reversible) within the same photon?
i.e. Is entanglement changeable between two photons?
i.e. can the experimenter play with coherence and entanglement with the same set of entangled photons?
i.e. decrease coherence and watch the effect of increased entanglement, Increase coherence and watch the effect of decreased entanglement?
6. In a single particle, double -slit experiment are the wave-functions passing through each slit assumed to be entangled with each other? in the case of an "in-coherent" photon?
 
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  • #2
1. Do incoherent photons interfere?
What do you mean with "incoherent photons"?
There are no photons you can point to and say "this cannot have interference".
You can get interference effects with all light, but if the different photons in that light are not coherent (to each other!), you might be unable to notice this.

2. Why does coherence increase when light is passed through a pin hole?
Depends on the setup. You select some specific part of your light, which might have some special properties (with the obvious one: "went through that hole").
3. Why does brighter light have higher coherence?
This is not a general rule. It might depend on the setup.
5. Can coherence be changed (is it reversible) within the same photon?
What do you mean with that?
i.e. Is entanglement changeable between two photons?
You can transfer entanglement between different photon pairs, and modify the entangled properties. If that does not answer your question, I don't understand it.
i.e. can the experimenter play with coherence and entanglement with the same set of entangled photons?
i.e. decrease coherence and watch the effect of increased entanglement, Increase coherence and watch the effect of decreased entanglement?
What do you mean with that?
6. In a single particle, double -slit experiment are the wave-functions passing through each slit assumed to be entangled with each other?
It is a single wave function.
 

FAQ: How Do Coherence and Entanglement Affect Photon Interference?

1. What is the difference between coherence and entanglement?

Coherence refers to the ability of a system to maintain a stable and predictable state over time. Entanglement, on the other hand, is a quantum phenomenon where two or more particles become interconnected and exhibit correlated behavior, even when separated by large distances.

2. How are coherence and entanglement related?

Coherence is necessary for entanglement to occur, as it requires the precise control and manipulation of quantum states. However, not all coherent systems exhibit entangled behavior.

3. What is the significance of coherence and entanglement in quantum computing?

Coherence and entanglement are essential for the success of quantum computing, as they enable the storage and manipulation of quantum information. Without these properties, quantum computers would not be able to perform complex calculations and solve problems that are intractable for classical computers.

4. How do scientists measure coherence and entanglement?

Coherence can be measured through techniques such as quantum state tomography, which reconstructs the state of a system by performing measurements on multiple copies of it. Entanglement can be measured through various entanglement measures, such as concurrence, which quantifies the degree of entanglement between two particles.

5. Can coherence and entanglement be observed in macroscopic systems?

While coherence and entanglement are typically associated with microscopic particles, recent research has shown that they can also be observed in larger, macroscopic systems. These systems, known as "macroscopic quantum systems," have the potential to revolutionize fields such as metrology, sensing, and information processing.

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