mechanics – what is it?
describes the laws and phenomena in the microcosmos,
among tiny particles and incredibly weak light,
photons. These laws do not always agree with our
common sense, nor do they fit in with our everyday
experience. For example, particles can move right
through matter and be in two places at the same
time. They are also affected when they are measured.
Nevertheless, the laws of quantum mechanics have
every time up to now been in agreement with experiments.
If anyone could demonstrate that quantum mechanics
does not work, it would be a truly revolutionary
part of Glauber's theory is that the laws of quantum
mechanics apply when measuring light. This means that
all measurement will always affect what is being measured.
Let us suppose that we want to measure where a photon
is with a number of light detectors alongside each other.
If we get a click in a detector, we know that at that
very moment the photon is just there. The problem is
that before the measurement the photon probably extended
over a much larger area than just the detector that
registered a hit. The measurement affects the photon
so that it is observed at a particular place.
to deal with this problem is to take many measurements.
In the end a pattern of how probable a particular result
is will emerge. This is what the diagram of the wave
pattern shows. Every detection of a photon is a measurement,
resulting in the photon being observed just there. A
few measurements alone seem to be random, but if we
collect many such measurements, a wave pattern emerges – a
picture of the properties of the photon before it was