Single Photon Emission: Examining the Evidence

[ndvcx]

On the web are some informed-sounding discussions saying that the various videos showing the appearance of the dots on the photo-sensitive surfaces can by no means guarantee that only one photon got through. A lot hinges on that, thanks for referring me to other posts which show certainty of a one-photon emission...so, packs of photons or just one ?

 

[cragar]

They have done it by shooting one photon at a time and they still get a double-slit interference pattern over time . I am not sure what your asking

 

[Dr Lots-o'watts]

Which experiments are you talking about? What discussions? What videos? What kind of photosensitive surface?

 

[torquil]

On the web are some informed-sounding discussions saying that the various videos showing the appearance of the dots on the photo-sensitive surfaces can by no means guarantee that only one photon got through. A lot hinges on that, thanks for referring me to other posts which show certainty of a one-photon emission...so, packs of photons or just one ?

Single photons.

Google will give any interested party links to masses of free info on the types of single-photon sources available.

 

[ndvcx]

Thx, can't find the page any more, it discussed the details of PMT. Also, there seems to be an admission that they have "background". Will try to post if I find it.

 

[Cthugha]

To the best of my knowledge nobody has ever performed the double slit experiment using single photons. To do that, you would need a single photon source and enlarge spatial coherence such that both slits lie inside its coherence volume. This can be achieved by placing it further away from the slits, which will of course also decrease the signal. As pretty much any detector with single photon sensitivity also has some non-negligible dark count rate, it would be pretty hard to get a signal count rate significantly higher than the dark count rate.

Most experiments claiming single photon interference used attenuated lasers or similar stuff which do not really give you single photons. However, this concept can be demonstrated much easier using single electrons instead of single photons and doing so works quite fine. This has been first demonstrated by Merli in 1974 and in better quality by Tonomura in 1989. See for example the Hitachi website (Tonomura worked for them in 1989) where also a video of these experimental results is shown:http://www.hitachi.com/rd/research/em/doubleslit.html"

 

[ndvcx]

Thx Cthugha. I've found some detailed experimental setups which describe how the slits are made microscopically tiny, and the attenuation greater and greater "until the (connected) oscilloscope reports only single electrons being dislodged.." or such. I've watched the hitachi video also. Your view (and mine, though mine counts less as non-physicist) is then a minority view, it seems, bec. the point of the experiment as it is generally accepted is to demonstrate interference of a photon with itself, and this is not taking place if there is a "pack"..