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Dr. Matthew Sellars stated that the objective for 'stopping' light is to develop memory for quantum computing. He said:
“Stopping light is not just a neat trick, it is the basis of a quantum memory — a device capable of storing and recalling the quantum states of light."
Here's how its done:
“We use a small silicate crystal doped with a rare-earth element, praseodymium. It is on the praseodymium ions that we store the light pulse. “When we shine a laser pulse at this crystal, it’s normally absorbed. The light doesn’t get through the crystal. Then we add a second laser beam that turns on the coupling between the nuclear spins and the light. This coupling makes the crystal transparent. So when we now fire the first laser beam at it, it gets through, but the odd thing about it is that it takes a very long time to do so.”
“To store the light in there, we turn the second laser beam off. The signal from the first laser beam is trapped inside the crystal. To get the signal out again, we turn the coupling beam on again. We can now store light for seconds, and potentially quite a bit longer."
(Dr. Matthew Sellars, Laser Physics Centre, in PhysOrg)
The next goal is to stop and store a single photon, creating the first quantum memory.
"And this stopping light, what we're doing is transferring the quantum information which is on the light, or a complete description of the light field.
"We can now store it on the crystal and hold it there for a long time, for seconds and hopefully longer, and then come back basically just flick a switch, and then recall that quantum information and regenerate the light pulse. "It should be an exact copy of the pulse that we've put in. So rather than using electrons we'll be using photons, we'll be using light pulses to control our computer system."