One of the enabling technologies for a quantum internet is the ability to store and retrieve quantum information in a reliable and repeatable way.
One of the more promising ways to do this involves photons and tiny clouds of rubidium gas. Rubidium atoms have an interesting property in that a magnetic field causes their electronic energy levels to split, creating a multitude of new levels. Switching the field off, returns the atoms to their normal state.
So one way to store photons, and the quantum information they carry, is to send them into a cloud of rubidium atoms and switch on the magnetic field. If the photons have a wavelength that is absorbed by the new electronic levels in the gas, they become trapped within it.
As long as the field remains on, that is. Switch the field off and the atoms are forced to emit the photons allowing the information they hold to be retrieved.
That immediately suggests a way of building a quantum memory.
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