Originally posted by humy
Is it possible to make a device that can detect single photons of radio waves with wavelengths of many meters even if they enter the device at a rate of no more than, say, one per second and, if so, how might it basically work?
I tried googling this but got nowhere.
I understand the main reason why radio detectors are not designed to detect single photon ...[text shortened]... use. But perhaps it could have a radio-frequency lens made of a metamaterial to get around that?
In a related field. I studied the effects of our local gravitational lensing from our sun and discovered an interesting effect: If you look at the long view of the sun, say go back a billion Km, and observe radiation being lensed by the sun, first thing you notice is that radiation focuses at around 1000 AU, roughly.
Now if you look at say, UV light, it comes to a nice crisp focus, at least on first look.
However, if you look at wavelengths say a million Km long, as that radiation goes by the sun, the entire gravitational lensing effect is very limited for such large wavelengths. So if you had a detector at the first focal point (it's really a focal line leading nearly to infinity, but that's another story) and you have a detector that can detect radiation say from wavelengths of 1 million Km down to UV or so, you will find a maximum wavelength that can be focused by the sun.
This leads to the idea that you could figure out the mass of a star by going to the first focal length, and just measuring the cutoff wavelength of radiation, assuming there IS million Km wavelength radiation floating around the universe
but a measure of such can tell you the mass of the star directly with no need for any other measurements.
One problem with the single photon measurement is that a naturally occurring set of wavelengths of such a low frequency, say less than one megahertz, is it is almost impossible to actually generate a single photon of such a wavelength. So you would be dealing with some kind of multi-wavelength radiation train. So your detector would have to be the one that could parse out one photon, some kind of switch that could, say, capture a single wavelength, say 1000 meters long, and direct it to a reflective box that could store that photon, in a way similar to the optical wavelength reflective capture devices, like a perfect set of mirrors that would let that photon bounce back and forth with no degradation so you could work with that photon for whatever reason you are after. At very low frequencies that might require say, a superconductive box that would allow that photon to be captured, and of course it would have to be very large to accommodate such a beast of a photon!
The detector I don't think would have to be as cold as you suggest although that would help. The main thing you would need would be reactive circuitry that would be sensitive to the wavelength you are after, some kind of tuned circuit that would in effect amplify a single frequency of interest. It would exactly amplify directly but be much more responsive to a single frequency than others and so preferentially capture the wavelength of interest.
So that's my 2 cents worth on the issue.