In a silicon crystal, the stuff of microchips, there sometimes sits a foreign atom, like magnesium. It behaves like a tiny magnet with several 'pointer positions.' If you illuminate such a crystal with a short flash of light, the atom momentarily gets excited, then returns to its ground state. But it doesn't do so instantly; there's a delay.
Scientists measured how the crystal's transparency changes after the light flash. It turns out that one of magnesium's excited states lives for about 20 milliseconds. For an atom, that's an enormous span, like a tossed ball hanging in midair for several minutes. The reason is that the atom must 'climb over' a small energy barrier to return to its ground state. This barrier is roughly 13 millielectronvolts — a tiny energy, but enough to delay the transition.
Such a long 'freeze' is useful for quantum technologies. If an atom can hold its state for a long time, it can serve as a memory cell in a quantum computer. Silicon is the primary material of modern electronics, and embedding such long-lived impurities into it is a step toward devices that operate by the rules of quantum mechanics.
The energy of 13 millielectronvolts is about a hundred times smaller than the energy carried by a single photon of visible light. Yet this tiny difference makes the atom wait 20 milliseconds before returning to its ground state.
In the series 'Westworld,' quantum states were used to store consciousness. Long-lived states of impurities in silicon are a real step toward such technologies.