Twisted light has transmitted information across 143 kilometres of open space — almost 50 times further than the previous record. The breakthrough could revolutionise how we communicate with satellites.
Light is an electromagnetic wave that has crests and troughs. It also has a property called phase, which governs when the crests or troughs reach a particular point in space. Normally, all the waves that make up a beam of light have the same phase, so their crests or troughs are in sync.
Not so with twisted light: different parts of a twisted light beam have different phases, making the beam appear to move like a corkscrew. The amount of twists in the corkscrew can be used to encode information.
Crucially, there is no theoretical limit to how many twists you can encode in a single beam, and hence no limit to the amount of information you can store in it. This makes it ideal for communications, especially with satellites. But atmospheric turbulence can disrupt twisted light.
In 2014, Anton Zeilinger at the University of Vienna in Austria and colleagues transmitted twisted light through the air over Vienna. They encoded enough information to send images of Mozart and Boltzmann.
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