Fiber-guided atoms preserve quantum states—clocks, sensors to come

An atomic clock based on a fountain of atoms. (credit: National Science Foundation)
One of light’s most redeeming features is that it can be guided in optical fibers with very little change to its properties. In terms of quantum information processing and sensing, this is important: you stick a bit of information into an optical fiber, and you will get that bit out the other end with very high probability. 
Matter is not so nice to work with, but the sensitivity that makes matter difficult also makes it promising for sensing applications and quantum computation. Researchers have recently demonstrated that matter can be guided down an optical fiber without losing its quantum state, opening up the possibility of combining the best properties of light and matter. 
A train track of quantum states
I think the atomic clock best demonstrates the benefits of moving quantum states around. In an atomic clock, we shoot atoms upward in a vacuum to measure the passage of time. The end result is measurement accuracy down to about 10 attoseconds (10-18s).
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