# Single slit single particle interference

1. Jan 10, 2012

### San K

If we send one photon, at a time, through a single slit do we observe the interference pattern? Specially at the edges

2. Jan 10, 2012

### Ken G

Yes, there is a diffraction pattern for a single slit. As with two slits, you see it best when the slit size starts to get smaller than the wavelength of the light, or the deBroglie wavelength of the particle (which is the same thing).

3. Jan 10, 2012

### Drakkith

Staff Emeritus
Ken, am I correct in assuming that the Airy Disk is also due to interference? Actually, is diffraction itself simply interference?

4. Jan 10, 2012

### Ken G

Yes on both counts. Perhaps if one was being very careful, one might say that diffraction is an observed phenomenon and interference is the mathematical description we use to understand it, but in that sense they're basically the same thing.

5. Jan 10, 2012

### Drakkith

Staff Emeritus
Awesome, thanks!

6. Jan 10, 2012

### San K

Thanks Ken. Could we create different interference patterns by creating phase differences in select parts of the "wave" of a single photon (in the above setup I.e. Single slit single photon at a time)?

7. Jan 10, 2012

### Ken G

Sure, anything you can do that will alter the phase of the wave will change how it interferes. That's essentially what interference is-- addition of amplitudes (affected by phase) that have had different histories so come out differently. Classically, we thought a "history" is something that a particle had, but in wave mechanics we find that the history actually belongs only to the amplitudes (which have magnitude and phase) being coadded to determine how the particles will behave.

8. Jan 10, 2012

### San K

We are playing with the wave of a single photon...while the photon (in particle form) cannot be split, its waves can (for example in the setup above or a mach zender etc.).

Interesting...can we say that all the information in the (known) universe is essentially coded in amplitues, phases, spins and spatial arrangements been photons and their constructs (molecules, galaxies etc)?

Last edited: Jan 10, 2012
9. Jan 10, 2012

### Ken G

Possibly, I guess that depends on how seriously we take quantum mechanics. Personally, I have noticed a historical trend that physicists of any era tend to imagine that their current theories embody truth in similar terms to that, and then later eras of physicists look back on them and say "how naive they were"-- then turn around and make the exact same mistake themselves!