Photon guns are important tools for engineers attempting to build the next generation of quantum communications gear.
They want to be able to create a single photon and fire it at will. And sure enough, there are a number of different technologies that allow them to do that. But aiming these photon gun so that the photons strike one target or another is much harder.
Now Yuntian Chen at the FOM Institute for Atomic and Molecular Physics in the Netherlands and a couple of friends have come up with a solution.
They point out that it is possible to force a photon gun to fire photons in a specific direction by placing it next to an antenna aimed that way. Such an antenna might consist of a line of metal particles of a certain size with a specific spacing. The way a photon couples to this antenna is highly senstive to the size of the particles and the refractive index of the medium in which they sit.
Chen and co’s idea is to create a line of silver particles each 55nm in radius and another line at right angles of larger particles with a radius of 58nm.
The photon gun sits at the point where the lines would meet and the entire array embedded in a liquid crystal that can change refractive index.
When the gun emits a photon, the light usually couples to the 55nm particles and heads off in that direction.
However, Chen and co say that when they change the refractive index of the liquid crystal, the light should couple to the larger 58nm particles and head off in that direction instead.
The result is a photon gun that can by aimed in one direction or another at the flick of a switch, something that will surely be handy for quantum engineers.
Ref: arxiv.org/abs/1007.1618: Dynamically Reconfigurable Directionality Of Plasmon-Based Single Photon Sources