Quantum fluctuations at radio frequencies

[f95toli]

It's a Quantum Mechanics issue because the energy to the antenna is that of one 50MHz photon. There is a center frequency to the sine pulse., which is 50MHz

No, thing don't become "quantum mechanical " just because you reduce the power,. Try the following "gedanken" experiment, Imagine a setup with a 50 MHz sine-wave signal generator that is outputting a perfectly coherent signal. If you connect this to a spectrum analyzer you will see a peak at 50 MHz. Now gradually reduce the signal; as you reduce the power the amplitude of the peak will decrease and if you had a perfect analyzer you could go on doing this forever. At some point you might start to observe the effects of shot noise because the of the "discrete nature" of the incoming photons, but other than that nothing special happens; you can keep going until the average number of photons per second become arbitrarily small.

Now imagine the same setup except that you introduce a pulse modulator after the generator. This "chops" the signal by turning it in and off at some rate. If you now send this into your analyzer. You will now observe lots of peaks ; both harmonics of the 50 MHz signal and other peaks at frequencies related to the modulation frequency and the rise and fall time of your modulator. Each peak corresponds to distributions of photons of different frequency reaching your analyzer. Hence, you no longer have a "pure" signal with photons of a a single frequency.
You can also reduce the power, but as long as you focus at a single peak it is exactly the same as for a continuous wave.

Here's a thought. Instead of sending one wavelength to the antenna, what if we send say 100 wavelengths, but set the energy per wavelength to 1/100th? That way the bandwidth is shorter, and according to Quantum Mechanics the probability is there that somewhere in the 100 wavelengths one photon will be emitted. This is what's wonderful about radio frequencies. We have amazing control over the current and signal. :)

Again, you can't send "wavelengths" into a circuit. That terminology does not make sense even in classical EM. A longer pulse will obviously result in a narrower frequency distribution, but why not then simply use a continuous wave?

The point is that creating single RF photons is very difficult, and it is very much an active field or research. The first experiment to demonstrate single microwave photons wa done only a few years ago; and there are several ongoing projects where people are trying to do this as efficiently as possible (I work on one such European project)

 

[Ponderer]

Honestly, one's definition of when something falls under a Quantum Mechanics is not so interesting to me. ;)

I think we get too caught up in frequency. Wikipedia says radiation resistance is caused by radiation reaction, which redirects to Abraham–Lorentz force, which in terms of an individual photon causes a spike, not sine wave. If a continuos sine wave current signal is produced in the antenna, then a sine signal is emitted. If it's a square wave given a certain bandwidth, then that's the signal that's emitted. Early this year I wrote some software that shows how spikes given the probability of producing a sine wave, say 50MHz, will produce a signal that has 50MHz in the spectrum even if on average there's only one spike every 1000 cycles. This is in reference to a continuous signal.

Anyhow I disagree with you on single radio wavelength photons. I think you're getting to caught up on trying to nail each photon down to a specific frequency. It's a packet of energy that has a spectrum given a starting and ending time domain, which changes depending on the FFT input time range even if it there's no trailing or leading signal. At radio frequencies it's very easy to limit the time duration of that packet of energy. :)

BTW I've sent you and Duck a private conversation message, but haven't heard from either one of you. Did you receive it?

 

[Ponderer]

For several months I've been designing a single radio wavelength photon experiment. Hopefully this thread can remain open until I publish the results.

If this thread closes, then you can periodically check my profile for a new thread. Or you could follow me, although I'm not sure if that would send you alerts if I start a new thread.

Soon we'll know for certain the results of this experiment. :)

 

[Ponderer]

I made a major improvement to the experiment that will allow us to tell if The_Duck and f95toli are correct. They're saying that even if thermal noise is low and not an issue, and if the antenna current is set considerably below the one photon per wavelength threshold, that photons will be emitted but just not every wavelength. So for example if the antenna current is set to 1/10th the level that produces one photon per wavelength, they are saying one photon is emitted once every ten wavelengths on average with a poisson distribution.

I disagree with them. Here's an example that clearly explains why I disagree. Imagine a stiff button. If you tap the button, then you can tap it a billion times till you're blue in the face and it's not going to press the button. Yes, normally I believe the photon would be emitted every so often in a classical way because thermal energy brings the antenna current beyond the threshold. But as started from the start of my experiment, there are resistors of high resistance that bring the thermal noise current significantly below the threshold. And hence the title for this thread. Will quantum fluctuations somehow cause the photon to emit even if thermal noise is too low?

Anyhow, hopefully soon we'll see the results of the experiment. Maybe within a week if all goes well.

 

[jtbell]

This thread is now closed, as per PF policy on (not) discussing unpublished research. When you publish your results in a professional peer-reviewed journal, feel free to use the "Report" link at the bottom of this post to ask the Mentors to re-open this thread if you want.