Single Photon Interference

"Can a single photon give interference pattern?"

The quantum physics guys should really answer this, but as far as I know, the answer is no!

As I understand it, if you fire many single photons (one at a time) through a type of "double slit" experiment, you will get an interference pattern, but not from (one) single photon!

But I stand to be slapped on the wrists (if justified)!

Yes, a single photon will produce an interference pattern. To use Jorries example, if you fired a single photon at a double slit you get an interference pattern on the other side. This is because Photons have both wave and particle like characteristics.

To understand why this is an indication of wavelike behavior, observe the double slit experiment below, which is done with water:

When the incident water wave hits the double slit, diffraction creates a new a wave pattern that appears to have two sources (where the slits are). These sources interfere producing a pattern. A photon does the same thing. Even a single one. This is one of many reasons why Quantum Mechanics is known to give rational people headaches.

Roger, I still have a problem with: "Yes, a single photon will produce an interference pattern."

Is there any observational evidence for one single photon that produced an interference pattern? I only know of many photons, fired one at a time, to produce interference patterns. Otherwise, explain it to me, where do I miss it?

I'm not rational - I just have this headache!

Jorrie,

Yes, it's been done experimentally with single photons, electrons, and other quantum mechanical particles. In all cases, there is an interference pattern. At this time there really is no explanation as to why they behave like this. Many (including myself) have pet theories, but there is no solid explanation for the bizarre behavior of Quantum Mechanical particles. Here are some links describing the phenomenon:

https://www.thoughtco.com/youngs-double-slit-experiment-2699034
http://www.canadaconnects.ca/quantumphysics/10083/

I hope these help.

Thanks Roger, will take a peek sometime!

Regards, Jorrie

I think the confusion results from the fact that the original experiment used a photographic film to record the results and it took quite a few events to adequately expose the film. But as I understand it from my reading, it is true for each event.

Thanks Roger, You have solved my problem.I was so much confuesd about this.

Ashish

This might lead one to the conclusion that photons are really not a single entity,but are composed of many even smaller packets that travel together as apparently one unit.Compare firing a shotgun at a double slit to firing a rifle at a double slit.

Over simplification,I am sure, but the same apparent result.I realize that "Common Sense" does not prevail at quantum levels, (and is apparently very rare at the macro level, also),but I believe you will get similar results.

Perhaps one day they will find that the photon,electron, and other particles are really like a swarm of bees traveling together.

Has anyone tried firing a single photon at a double edge, instead of a slit, to observe if it "splits?" into smaller packets? Will it choose one side or the other,or both?

Just Curious.

I think you are perfectly right.. .one photon doesnt give a pattern.. the pattern builds up with time!

The pattern is there for each electron. It is an interference pattern. If each electron, sent one at a time, only goes through one slit then it would have to time travel to interfere with the previous electrons. Each electron goes through both slits because it exists as a wave function. In the original pattern, it took numerous electrons to adequately expose the film used to record what was happening. The entire purpose of the experiment it to prove that the electron has a wave function that passes through both slots simultaneously. If you deny this then you must also deny the interference pattern that results unless you believe in time travel or magic as the cause. If you think about it you will see there is no other explanation.

What are the critical dimensions of the slits and the spacing between them?

What is the thickness of the material with the slits?

What effect does the slit dimensions and orientation (parallel vs skewed?) of the slits have on the results?

How far is the target from the slits?

I don't know the details. I'm sure a quick search online would turn up information. If I had to guess I would say: As narrow as possible. As thin as possible. No. It only changes the resultant pattern. Not critical, the effect will be larger but dimmer with increasing distance.

Time travel?What is time to a photon,moving at velocity of C?

Time stands still at C,right?A photon exists in all phases of time:Past,present and future.

It can actually be in two places at the same time (our time reference frame ).

Quantum theory is ever "curiouser and curiouser" as Alice said.

Here is a link to a quantum computer that solves a problem before it is even allowed to run,simply constructing it was enough.

Eventually, at that rate, all of our questions can be answered with nothing.

http://www.physorg.com/news11087.html

And after all what difference does it make anyway. Life accelerates entropy locally but outside the time bubble of our existence it is a net zero game and we already have a pretty good idea what the temperature is going to be in the end game.

I would assume that the total power delivered to the target is the same for a single photon thru one slot as it is for two slots.If true, then 1/2 of the power comes thru each slot.

Has anyone tried 3 or more slots? Different shapes;circular,triangular,etc.?

If it is truly a wave, 3 slots should give a different pattern,especially if spaced differently.For how many slots does this effect hold true?

Is the experiment conducted in a vaccum to eliminate interference with air molecules?

At the level of a photon,molecules could have a large effect.Imagine a strong oscillating wind between a rifle muzzle and the target.The projectile could be deflected and actually "split" by the divider of the slots.Perhaps the ZPEF has an effect?

Assuming that the photon is an indivisible packet of energy may be misleading.