"For this particular experiment, researcher Georg Heinze and his team converted light coherence into atomic coherences. They did so by using a quantum interference effect that makes an opaque medium — in this case a crystal — transparent over a narrow range of light spectra (a process called electromagnetically induced transparency (EIT)). The researchers shot a laser through this crystal (a source of light), which sent its atoms into a quantum superposition of two states. A second beam then switched off the first laser, and as a consequence, the transparency. Thus, the researchers collapsed the superposition — and trapped the second laser beam inside."
Here's why I bring it to your attention. Physicists Georg Heinze, Christian Hubrich, and Thomas Halfmann of the Technische Universität Darmstadt in Germany have succeeded in stopping light in its tracks for an entire minute. This astounding achievement has implications for building light-based quantum memory (which I also don't understand). But here's what blows my mind: In that one-minute span during which the beam of light was "frozen," it could theoretically have traveled about 11 million miles (18 million km), or 20 round trips to the moon.