Can a single particle be thought of as a wave? I don't have a direct reference but I read that Dirac once remarked, “a photon can only interfere with itself”.
But I recently came across a website in which it is written

The manifestations of wave-like behavior are statistical in nature and always emerge from the collective outcome of many electron events. In the present experiment nothing wave-like is discernible in the arrival of single electrons at the observation plane.

Is there a contradiction between the view expressed by Dirac and the view expressed in the website? Or am I mistaken?
 A: No contradiction, actually. When you detect a particle you get one dot. For instance, x-rays directed at a crystal, which are scattered on to a phosphor screen and a camera records the image. X-rays, neutrons, or other particles can be delivered slowly enough that they visibly come one at a time. BUT... if you keep the experiment going long enough, if you record enough dots, you will see the diffraction pattern. If the particles are coming one at a time, but collectively show a diffraction pattern, they can only be interfering with themselves because there is nothing else for them to interfere with.
Here is an example x-ray diffraction pattern from Eastman Kodak. You can see how it is composed of individual pixels, each one representing one x-ray detection. And those x-rays came one at a time, they didn't come all at once and interacting with each other.

A: The fact that a beam of photons or electrons can produce an interference pattern with dimensions measured in centimeters, leaves no doubt that they have wave properties, and if you want to read a book on quantum mechanics you need to be comfortable with wave equations expressed as imaginary functions.  The particle idea is associated with the fact that all of the energy and momentum of a “wave packet” (such as a photon) can be absorbed by an entity the size of an atom atom or smaller.
