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

One Photon from coil and battery

  1. Nov 18, 2007 #1
    I need only one photon from a coil and battery set up.

    Anyone know how I can get just one photon?
    e.g. 1) slowly increasing ramp voltage that spits out single photons slowly?
    2) Send a tiny voltage in by pushing a switch?
    3) Have many windings or just a few?

    Any clues please, would be most grateful. How does E = hf apply to a coil exactly?


    Attached Files:

  2. jcsd
  3. Nov 18, 2007 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    You cannot create "single photons" this way. All single-photon sources are created via energy transition, not 'classical' setup like this.

  4. Nov 18, 2007 #3
    I need just one photon

    But a coil would release photons, so cannot I get just one?
    Say, I make a 'step' by applying a step voltage to a coil? or
    filter the stream somehow (but how?)

    I must have some basic misunderstanding of school physics if
    only atom energy transitions allow me to get a single photon.
  5. Nov 18, 2007 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    There are no physics in which to apply to the technique that you are describing that can get you one photon at a time.

  6. Nov 18, 2007 #5


    User Avatar
    Science Advisor
    Gold Member

    It is indeed impossible to generatore single photons this way. There are many reasons why; but one "obvious" problem should be the energies involved. Try calculating the energy of a photon (in a setup like this the relevant frequency is probably a few hundred kHz at most) then compare that number to the energy in the coil.
    Even if you could generate a number state (i.e. a state with a definite number of photons, e.g. 1) you would end up with an enormous amount of photons, not one.
    As an excersise you can also try calculating the number of photons generated in the same frequency range due to the thermal radiation (because the coil is at room temperature and not at zero kelvin).

    I should perhaps point out that it IS possible to generate single photons using electrical circuits, i.e. high-quality microwave resonators operated at very low temperatures, but you need some pretty sophisticated equipment.
  7. Nov 18, 2007 #6
    Yes, thanks f95toli, I calculated that even for a very low inductance coil the current needed to produce one photon is thousandths of a microamp. My yellow plastic voltmeter does not go that low and, as you righlty say, thermal photons would be everywhere messing my experiments up - the little wrigglers!

    Here's my calculation (its only a rough measure of current needed to produce
    one phorton in a very small coil at 100 KHz)

    e = hf joules (for one photon_
    = 100*1000*6.63*exp-34 joules
    = 6.63*exp-29 joules
    = LI2/2 -for a small air coil at VHF
    i = root (2*6.63*exp-29/L)
    3 turns of lentgh 10 mm and radius 5 mm = 0.018443 µH
    i = root(2*6.63*exp-29/.02*exp-6)
    = root(6.63exp-21)
    = 8exp-11 amps wow, thtas small
  8. Nov 26, 2007 #7
    even if you can produce a single photon (in , how could you detect that photon? to improve that if it is true or not
  9. Nov 26, 2007 #8


    User Avatar
    Science Advisor
    Gold Member

    In this case it would be difficult (probably impossible) since the frequency is so low. However, once you reach a a frequency of a few terahertz (far infrared) good single photon detectors are readily available.
    There are also detectors that can operate down to a few tens of GHz (something like 90 GHz) and at least in principle detect a single photon.
  10. Dec 1, 2007 #9
    Single Photon Detector

    You mentioned single photon detectors are readily available.
    I am not in a School/University scene at present, so where can I get
    them privately? I suppose one that would go with a red laser?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: One Photon from coil and battery
  1. Two slits, one photon (Replies: 25)

  2. One photon at a time (Replies: 6)