Is this "cloaking in time" serious and what is really meant? I just found this news article: http://www.nature.com/nature/journal/v481/n7379/full/nature10695.html
What did those researchers actually do? The article itself doesn't sound to me like it can be taken seriously, so... what was the experiment and what was observed?
 A: I do not understand all the nitty details, but the gist goes as follows:
You have a constant probe beam, which is cast on a sample and analysed later.
Suppose the sample has a very predictable behaviour, with an event every $24\mu \text{s}$. Then the analysis of the beam will show exactly that. This is the blue line in Fig. 4.
Now, suppose you want to hide these events, but you don't want to divert the beam around the sample (for whatever reason). They do it in the following way:


*

*Increase/decrease the wavelength of that part of the probe beam, which would encounter the event. This only serves as "marking" the part of the wave you want to manipulate.

*Speed up waves with lower frequency and slow down waves with higher frequency. This creates a beam gap in the middle. That means, the sample will see the probe beam "turned off" during the event, and the probe beam is not affected.

*After the sample, reverse step 2, i.e. slow down waves with lower frequency and speed up waves with higher frequency.

*Reverse step 1. Now your probe beam looks roughly as if it was not messed with at all and probed the sample at all times.


Note, that this is a layman explanation, and the actual speeding up/slowing down is a rather complicated feat.
