The notion of quantum gravity has mystified many physicists, not least because there has never been a prospect of measuring the fabric of  the universe on this scale. That looks set to change.

A few years back, a number of physicists suggested that atom interferometry might do the trick. The thinking was that two atoms sent on different routes of equal length through space would then be made to interfere.

If spacetime is smooth and neat, the atoms should produce a certain set of fringes. But if spacetime on the plank scale were to be a maelstrom of quantum fluctuations, then these would force the atoms to travel slightly different paths and that would be picked up by the interferometer.

Sadly, it turns out that atom interferometers are nowhere near sensitive enough to detect these fluctuations and unlikely to become sensitive enough any time soon. The reason is that every three orders of magnitude increase in the sensitivity of the interferometer gives you only one order of magnitude increase in your ability to spot the fluctuations.

Which is why an idea floated by Mark Everitt and pals at the University of Leeds looks interesting. They say that the scaling problem effectively disappears if you use entangled atoms instead of ordinary ones.

And the improvement is such that the effect of quantum gravity should be detectable with current quantum optics technology.

They fall short of making any predictions so let’s fill in the blanks for them: somebody with a decent quantum optics lab will spot the first evidence of quantum gravity in 2009. Betcha!

Ref:  arxiv.org/abs/0812.3052:  Dephasing of entangled atoms as an improved test of quantum gravity

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