Splitting photons are entangled?

Click For Summary

Discussion Overview

The discussion revolves around the concept of photon entanglement, specifically focusing on the processes involved in splitting or downconverting photons. Participants explore whether photons can be split using various mediums, the role of beta barium borate (BBO) crystals, and alternative methods for achieving entanglement.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions whether splitting photons can lead to entanglement and asks if BBO crystals are necessary for this process.
  • Another participant clarifies that photons are not actually split; rather, in the case of BBO, a photon excites the crystal, resulting in the emission of two new photons.
  • A participant expresses curiosity about whether parametric downconversion can occur in mediums other than crystals and seeks alternatives for splitting photons.
  • It is noted that positronium annihilation can produce entangled gamma photons, suggesting that there are other mechanisms for generating entangled photons beyond BBO crystals.
  • Participants discuss the nature of the process in BBO, emphasizing that it involves virtual absorption and the polarization of the medium rather than a straightforward absorption and reemission of photons.
  • Some participants mention other methods for generating entangled photons, such as using optical parametric oscillators (OPO) and parametric scattering in polariton systems.

Areas of Agreement / Disagreement

Participants generally agree that photons do not split in the traditional sense and that BBO crystals are a common method for generating entangled photons. However, there is disagreement regarding the necessity of crystals for parametric downconversion and the existence of alternative methods, indicating multiple competing views.

Contextual Notes

Some participants highlight the complexity of the processes involved, including the nuances of virtual absorption and the conditions under which entangled photons can be generated. There is also a lack of consensus on the best methods for achieving photon entanglement.

ice909
Messages
5
Reaction score
0
I'm sorry if this is a silly question and please forgive me but, if you split photons into two by any medium or matter can it entangle photons? Do the photons have to go through a beta barium borate crystal or any other crystals? Are there any alternatives to split photons? Please provide good info and please no negative comments. Thank you.
 
Physics news on Phys.org
What do you mean by 'splitting photons'? Photons are never 'split'. Downconversion, occurring at BBO crystal is not a 'split': the photon just excites the crystal, which then emits pair of photons.
 
what i mean is that when a photon goes in the crystal, it splits right? what I am asking is that can i do parametric downconversion on any other medium or matter and can it split with that option? i don't have anything in mind, I am just curious.

here is the source where i got the information about splitting photons:


http://www.davidjarvis.ca/entanglement/quantum-entanglement.shtml
 
Last edited by a moderator:
Photons do not 'split'. What happens in BBO is that original photon is absorbed, and two brandly new photons are emitted.
BBO crystal is not the only means (but most common for practical purposes of experiments in optical range) to create entangled photons.

For example: if the positronium annihilates into two gamma photons - they are also perfectly entangled.
 
so, I am guessing that there is no other option to entangle photons. last question, do we have to use crystals to do parametric downconverison or is there a alternative, if so why?
 
xts said:
Photons do not 'split'. What happens in BBO is that original photon is absorbed, and two brandly new photons are emitted.

Strictly speaking they are not absorbed and reemitted. As this is a parametric process there is virtual absorption at best and no real absorption. A more solid description is given when examining the polarization arising inside the non-linear medium which is basically the eigenstate of the em field inside that medium. As the polarization contains non-linear response the possibility for sum- or difference frequency generation opens up and one can get down-conversion.

ice909 said:
so, I am guessing that there is no other option to entangle photons. last question, do we have to use crystals to do parametric downconverison or is there a alternative, if so why?

Ehm, as xts already said there are other possibilities. You could also use other parametric processes like the output from an OPO. Also there are schemes that rely on parametric scattering to generate entangled particles, especially in polariton systems.
 

Similar threads

Undergrad Determination of entanglement by observing only one photon
  • · Replies 20 ·
Replies
20
Views
3K
Undergrad Is it possible for a BBO crystal to produce an interference pattern?
  • · Replies 1 ·
Replies
1
Views
2K
Graduate What happens when entangled photons are split into different paths?
  • · Replies 41 ·
2
Replies
41
Views
7K
Graduate Is delayed choice remote entanglement of photons derived from TDSE?
  • · Replies 58 ·
2
Replies
58
Views
5K
Undergrad Are two entangled photons described by the same wavefunction?
  • · Replies 6 ·
Replies
6
Views
2K
Graduate Question about SPDC (Making entangled photons)
  • · Replies 1 ·
Replies
1
Views
2K
Undergrad Laser Beam through Calcite crystal = Photon Entanglement?
  • · Replies 2 ·
Replies
2
Views
3K
High School The setup of "2012 entanglement between photons that (....)"
  • · Replies 25 ·
Replies
25
Views
3K
High School Beginner Question Regarding Entanglement
  • · Replies 19 ·
Replies
19
Views
2K
Graduate Do you have to use a Beta-barium borate crystal in order to entangle photons?
  • · Replies 2 ·
Replies
2
Views
2K