Single particle single slit interference - question about the experiment

In summary, the referenced experiment involved a double-slit system where only one slit was open at any given time. It was shown that interference could still be observed if the path difference allowed for the detected photon to have come from either slit. This was achieved by using a phase shift in the two paths, with one slit having a longer path length due to an equivalent delay. The interference pattern appeared at a range of points where a path from both slits was possible, and it was best visualized at infinity as a function of angular position from the slits. It is possible that something physical is traveling through all the paths, but this is not certain and further analysis is needed.
  • #1
San K
911
1
Came across the below experiment, on Wikipedia, but don't understand how it was performed...

It was shown experimentally that:

in a double-slit system where only one slit was open at any time, interference was nonetheless observed provided the path difference was such that the detected photon could have come from either slit.

The experimental conditions were such that the photon density in the system was much less than unity.

Question: if only one slit is open --
how is the path difference created?
how could the photon have come from either slit?


Reference is:

Sillitto, R.M. and Wykes, Catherine (1972). "An interference experiment with light beams modulated in anti-phase by an electro-optic shutter". Physics Letters A 39 (4): 333–334. Bibcode 1972PhLA...39..333S. doi:10.1016/0375-9601(72)91015-8.
 
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  • #2
Guessing from the title ...
It looks like they used a phase shift in the two paths. The thing to remember is that the photon paths are paths through space and time.

Try it this way, imagine a regular double slit experiment but with a shutter opening the two slits for a very short time.

Now let one slit be farther forward and let its shutter therefore open and close earlier so that both slits are never open at the same time.

Next, instead of moving one slit forward, instead put an equivalent delay I the path to that one slit. This is what It sounds like they did.
 
  • #3
jambaugh said:
instead put an equivalent delay I the path to that one slit. This is what It sounds like they did.

Good guess jambaugh, thanks.

And is the delay equal to one wavelength (or some multiple) so that coherence is maintained between both the paths? to get interference
 
  • #4
San K said:
Good guess jambaugh, thanks.

And is the delay equal to one wavelength (or some multiple) so that coherence is maintained between both the paths? to get interference

Possibly a quarter wavelength so one path's peak equals the other path's node. That would effect a shift in the interference pattern but you'd still get the double slit interference.

and again speculating from the title, the "slits" would be optically controlled, say with a laser so that as the peak passes it opens (or closes) each slit in turn.
 
  • #5
jambaugh said:
Possibly a quarter wavelength so one path's peak equals the other path's node. That would effect a shift in the interference pattern but you'd still get the double slit interference.

well said...

jambaugh said:
and again speculating from the title, the "slits" would be optically controlled, say with a laser so that as the peak passes it opens (or closes) each slit in turn.

ok...open just in time to allow the peaks to pass through?
jambaugh said:
Now let one slit be farther forward and let its shutter therefore open and close earlier so that both slits are never open at the same time.

Next, instead of moving one slit forward, instead put an equivalent delay I the path to that one slit.
does the interference start (to happen/evolve) at the second/further/delayed slit?
 
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  • #6
San K said:
ok...open just in time to allow the peaks to pass through?
Right.
does the interference start (to happen/evolve) at the second/further/delayed slit?
The interference pattern will not show up you've at a range of points where a path from both slits is possible. It is better, I think, to visualize the interference pattern at infinity, i.e. as a function of the angular position from the slits.
 
  • #7
jambaugh said:
The interference pattern will not show up

?...we just agreed that there would a shifted interference pattern...

jambaugh said:
you've at a range of points where a path from both slits is possible. It is better, I think, to visualize the interference pattern at infinity, i.e. as a function of the angular position from the slits.

not sure what you are saying...however you have piqued the curiosity

do the range of points start post (or prior) the second/further/delayed slit?

if we were to place a screen after the second/further slit, we would see an interference pattern and as we move it backward the pattern would continue to show up

however if we moved the screen closer...and before the second slit (i.e. between the first and second slit)...i guess we would not see an interference pattern...right?

the actual experiment might not be done that way...however the above analysis can still be done, i guess...

does it not seem as if something is physically traveling through all the paths?
 
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1. What is single particle single slit interference?

Single particle single slit interference is a phenomenon that occurs when a single particle, such as a photon or electron, passes through a single slit and interferes with itself, creating a characteristic pattern of light or dark fringes on a detection screen.

2. How does the experiment for single particle single slit interference work?

In the experiment, a single slit is placed in front of a detection screen. A source emits particles, such as photons or electrons, one at a time through the slit. As the particles pass through the slit, they diffract and interfere with each other, creating a pattern on the detection screen. This pattern is then recorded and analyzed to understand the behavior of the particles.

3. What are the key factors that affect the outcome of the experiment?

The key factors that affect the outcome of the single particle single slit interference experiment are the wavelength of the particles, the size of the slit, and the distance between the slit and the detection screen. These factors determine the amount of diffraction and interference that occurs, ultimately affecting the pattern on the detection screen.

4. What is the significance of single particle single slit interference in quantum mechanics?

Single particle single slit interference is a fundamental concept in quantum mechanics. It demonstrates the wave-particle duality of particles, where they can behave as both waves and particles. This phenomenon also highlights the probabilistic nature of particles, as the exact location of a particle cannot be predicted, only the probability of it being in a certain location.

5. How is single particle single slit interference used in practical applications?

Single particle single slit interference has practical applications in fields such as optics, electronics, and quantum computing. It is used to measure the properties of particles, such as their wavelength or energy, and to create diffraction patterns for various purposes. Additionally, this phenomenon is crucial in understanding and developing technologies that utilize quantum mechanics, such as quantum computers.

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