For the first time, a device has created a "hole in time" -- for a few nanoseconds anyway.
The theoretical possibility of an "event cloak" -- a metamaterial space-time device that could theoretically conceal an entire event in time from the view of an outsider -- has been written about for years. And while some bright minds have been talking about bending space-time to their whims, a team at Cornell was doing it. And it works. For 110 nanoseconds.
Basically, you need two time-lenses -- lenses that can compress and decompress light in time. This is actually possible to do using an electro-optic modulator (what, you don't have one?). Two of these modulators can slow down or compress the light traveling through the first lens; a second lens downrange from the first can then decompress, or accelerate, the incoming photons from the first lens.
Think of the photons like steadily flowing traffic on a highway. If you slow the traffic at a point upstream, you create a gap. You can cross the highway through the gap and then accelerate that traffic to catch up to the traffic ahead, closing the gap. To someone further downstream, the gap isn't there -- to that observer, the gap might as well have never existed because there's no evidence of it.
During that gap, whatever occurs goes unrecorded. But you'd have to be pretty quick were you to use such a device to pull some kind of shenanigans. The current gizmo the Cornell gents have built creates a 110 nanosecond event gap, and they concede that the best it could achieve is 120 microseconds.
But as Technology Review notes, rarely is anything final in cutting edge theoretical physics.