Photons are the workhorses of modern communication. At present, they generally carry information in light pulses consisting of many photons but physicists are already able to use single photons instead, encoding data in their very structure.
One way of doing this is to use the photon’s orbital angular momentum, a measure of its helicity. So instead of travelling as an ordinary flat wave, the photon can be thought of as a helix with left or right handedness that is twisted to varying degrees.
Physicists can use this handedness and the amount of twist to encode data in the very shape and structure of the photon itself. This has big advantages over the way physicists exploit photons today.
The conventional way physicists do this is using polarisation. A photon can have two distinct polarisation states–either horizontal or vertical. It’s straightforward to create photons in one state or the other and use this to encode data.
The big advantage of orbital angular momentum is that a photon can be produced in an infinite number of different states of handedness and twistedness. That means a single photon can carry an arbitrarily large amount of information, in principle a least.
So it’s no surprise that researchers are eagerly exploring ways of creating and detecting photons with varying spatial structures that can carry information.
But what they’ve lacked is a way of storing these photons–including their detailed shape and structure–and then releasing them again later.
Today, Dong-Sheng Ding and pals at the University of Science and Technology of China in Hefei say they’ve cracked this problem for the first time.
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