Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

B Is entanglement preserved on re-emission of photons

  1. Feb 10, 2016 #1
    What happens if I create entangled photon pairs and then pass them through a phosphorescent coating so they are absorbed and re-emitted?

    Is entanglement preserved?

    In my case, I have succeeded and created UV entangled photon pairs in my latest experiment but I could not see them with my naked eye so I used a phosphorescent coating to convert them to visible frequency.
  2. jcsd
  3. Feb 10, 2016 #2


    User Avatar
    Science Advisor
    Gold Member

    Really? What led you to this conclusion? Did you do any tests to confirm this? If so: can you describe the tests?

    Or are you simply making an assumption?
  4. Feb 10, 2016 #3
    I repeated the experiment from an online science journal about getting these photons from mercury lamps. Mercury and calcium have an excited state with zero momentum and so is the ground state of each atom. The decay is double and the particles obtained are entangled.


    I know it for certain. But I want the answer to my question - is the entanglement preserved?
  5. Feb 10, 2016 #4


    User Avatar
    Science Advisor
    Gold Member

    The reference does not indicate entangled photons are generated. They show the theoretical ability to create quantum phenomena, but little else.

    Regardless, before you start telling us that you are generating entangled photons: tell us how you know for certain. You cannot make exaggerated claims and expect that they will not be challenged. I would recommend you retract your statement.

    As to your question: What do you think? And why do you think it? Are phosphorescent photons going to retain their polarization through the process? What is phosphorescence? What are the intermediate electron states?
  6. Feb 10, 2016 #5
    You missed the parts of the reference that contain the sentences

    "Various ways can be used to generate entangled photons capable of exciting luminescent materials. Cascade atomic emission of photons can be used. Commonly used are the photons emitted by mercury lamps."

    "Aluminate pigments and Zinc Sulfide pebbles were quantum entangled via photoexcitation with entangled photons from a mercury lamp"

    And you missed this

    https://books.google.ro/books?id=Gl...E#v=onepage&q=mercury atoms entangled&f=false

    "From about 1990 onward, experimentalists replaced the calcium and mercury atom sources for entangled photons with a device called a spontaneous parametric down-converter."

    See? Another reference telling mercury and calcium are sources of entangled photons.

    https://www.quora.com/Why-does-excited-calcium-emit-entangled-photons-rather-than-unentangled-photons [Broken]

    "The excited state of calcium atom, that is used as entangled photon source, has zero angular momentum (J). As the ground state of a calcium atom also has J=0, angular momentum conservation forbids direct transition with single photon emission, as photon has spin 1. So the state decays with emission of two photons, via an intermediate J=1 state. As the intermediate state has very short lifetime, too short for any interaction to affect the direction of its spin, the spins of emitted photons must sum up to zero. This makes them entangled."
    Last edited by a moderator: May 7, 2017
  7. Feb 10, 2016 #6


    User Avatar
    Science Advisor
    Gold Member

    No, I didn't miss anything. I keep telling you: having a mercury lamp does not mean you have entangled photon pairs. It is much more complicated than that. If you think these scientists just turn on a lamp and start counting, you are mistaken.

    You must do a lot more. It is discouraging to see someone so obviously interested in the science ignore the details in the references. The details are the hard part, and they are critical.
  8. Feb 11, 2016 #7
    As much as you would want mercury atoms to emit single independent photons, they cannot because their electronic shell forbids them to. Angular Momentum has to be conserved between the excited state J = 0 and the ground state J = 0.

    The other part is that not any two emitted photons from a mercury lamp are entangled, only the photons emitted by the same atom. But I don't care about that in my setup.
  9. Feb 11, 2016 #8


    User Avatar

    Staff: Mentor

    You are talking too much and listening too little in this and some other threads.
    This thread is closed.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook