Re: Destructive interference of two photons

Nick,

Photons belong to the world of quantum mechanics, which follows rules that don't translate well to "everyday world" thinking. When considering a collision between pulses of light, you have to consider how both the wave and particle properties of light work. The propagation (transmission) of light is described by a wave function which gives the probability of detecting a photon (particle of light) at any specific point in space at a given time. In your scenario, two short pulses of light cross paths, each with only enough energy to produce a single photon. Each light pulse can be described as a "wave packet" which propagates through space in a single direction. At the point in space where their paths cross, we will let their wave functions cancel each other.

Now, this cancellation only means that if you try to measure a photon at that point in time and space, there is zero probability that you will find one. It is the same as looking at a dark band in an interference pattern. But that does not mean that the light no longer exists. Both wave packets will continue to propagate in their original directions, and soon their wave functions will no longer cancel. You will once again be able to measure photons from each packet.

Sorry about my delayed response. I hope this answers your question. Feel free to contact me at silver@physto.se if I can be of further help.

Regards,

Sam