In the context of the double-slit experiment with single photons, the interference pattern observed can be explained without invoking the concept of an "unseen anti-photon." The double-slit experiment is a fundamental experiment in quantum mechanics that demonstrates the wave-particle duality of particles.
When a single photon is sent through a double-slit apparatus, it behaves as a wave and exhibits interference effects. The wave nature of the photon allows it to pass through both slits simultaneously and interfere with itself, creating an interference pattern on a screen behind the slits.
The interference pattern arises from the constructive and destructive interference of the photon waves. When the peaks (crests) of the waves coincide, they add up and create bright regions on the screen, known as constructive interference. Conversely, when the peaks of one wave coincide with the troughs (low points) of another wave, they cancel each other out, resulting in dark regions, known as destructive interference.
This behavior can be explained by considering the probability amplitudes associated with each possible path the photon can take. The probability amplitude describes the likelihood of the photon being detected at a particular location on the screen. The amplitudes for each path interfere with each other, leading to the observed interference pattern.
There is no need to introduce an unseen anti-photon to explain the interference pattern. In quantum mechanics, the wave function, which describes the photon's behavior, is a superposition of all possible paths, and it accounts for the interference effects. The interference pattern arises from the probabilistic nature of quantum mechanics and the wave-like behavior of particles, without the need to posit the existence of an anti-photon interacting with the photon.