Photon by photon?

[vlad777]

I have heard that if you have a light source and put enough dimming filters
but not too much, you get photon by photon emission.

Now do I get the same effect with a LED if I put a big resistor in series with it?

I am guessing it would slowly charge and when there is enough energy
it would emit one photon and deplete energy so it has to charge
again for the next photon.


Many thanks.

 

[vlad777]

Another question:

Could I use avalanche photo-diode to detect a single photon, and how do I go about it?

 

[jpanhalt]

I think you need to address your second question first. How do you intend to detect single photons? Have you done any reading on photon counters?

John

 

[vlad777]

I saw on BBC Horizon double slit experiment done with photons. For the detector they had some kind of grid or camera.
It looked simple and something made me believe I could do it also.

Thanks, now I have a phrase "photon counter" to google.

 

[fernando_g]

I think you need to address your second question first. How do you intend to detect single photons? Have you done any reading on photon counters?

John

The closest application I can think, is CCD sensors used in astro-photography.

For starters, these sensors have to be cryogenically cooled to reduce leakage currents and noise.

Special techniques to deal with femtoampere level currents are required, but I ignore what they are.

 

[vlad777]

This looks expensive:
**broken link removed**

This article makes me think it's possible:
https://en.wikipedia.org/wiki/Single-photon_avalanche_diode

Is there a cheap way?

EDIT:

This idea of mine is coming from Seth Lloyd saying somebody did this for a dollar, and they used a LED diode.
This is that lecture: https://www.youtube.com/watch?v=_oBgnTy85fM
In this lecture there is a lot of fun stories and less material covered.
I recommend it.

@fernando_g

I am guessing they use those special CCD because they need an (hi-res) image.
I am thinking much smaller, just to create and detect a single photon in cheapest way.

 

[jpanhalt]

Cheap? What about just using your eyes? You cannot perceive single photons, but you might do OK with 40 or 50 in a burst.

https://math.ucr.edu/home/baez/physics/Quantum/see_a_photon.html

We used LN2-cooled photomultipliers to improve upon what we could perceive visually in the 1960's. But that is not cheap. I was hoping that some newer solid state devices may exist. They and their associated electronics may still need to be cooled to decrease noise.

John

 

[vlad777]

Interesting read.

But to answer your question, people can use their brain to do arithmetic, but we still make calculators.

 

[unclejed613]

part of your problem is going to be having the photodetector in the path of the photon. also, the energy level of the photon is very important. with a given detector, you may be able to detect a gamma or X-ray photon, but not one in the visible spectrum. one application where the ability to count single photons is important is in fusion research, where you want to be able to count how many fusion reactions take place. this is done by counting the gamma and xray photons emitted by a target in the path of the high energy neutrons from the reaction. many detectors in use will detect such photons, but the photons from visible light may not be energetic enough to be detected.

this is how people testing the "cold fusion" apparatus back in the 80's knew there wasn't any fusion taking place. the D2O in the apparatus should have emitted neutrons when the deuterium nuclei fused into helium. but without neutron emission, 1)the reaction is not sustainable, even if it does occur on a small scale, and 2) a byproduct of fusion reactions is neutrons, because some of the reactions will create 3He with the loss of a neutron and another byproduct of the reaction could be 3H (tritium), which will then fuse with 2H (deuterium) to form 4He, with, again, the emission of a neutron.

however, fusion in a Farnsworth-Hirsch fusor emits a LOT of neutrons, indicating there is fusion taking place in the reaction.

 

[vlad777]

Update.