Quantum mechanics is a realm of weirdness: electrons being
linked to each other even though the vastness of the universe
might separate them, things being in two places at once, and, of
course, knowledge precluding knowledge. This last is the
standard bearer of quantum oddity: measuring the momentum of an
object precludes precise knowledge of where that object is. But
I think I have found something that is stranger than them all.
Researchers have suggested that it might be possible to make
measurements that trick a photon into thinking it is, in fact, a
crowd of photons. Let's imagine that we want to introduce a
phase shift to one single photon through a control photon. A
phase shift is basically a time delay. In traditional optics
this delay is applied through high-intensity light beams: a high
intensity pulse can modify the refractive index of the medium
through which it propagates. Our signal photon traveling through
that medium will see that different refractive index and either
be delayed or sped up. The