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Physicists harness atomic 'dark states' to store light - Livescience.com
Jun 09, 2021 1 min, 36 secs

Physicists have achieved a phenomenon known as subradiance, in which atoms linger in an excited state, in a dense cloud of atoms for the first time. .

Atoms gain energy by absorbing photons (light particles) that cause their electrons to jump from the lowest-energy "ground" state to higher-energy excited states?

Once they're in an excited state, atoms spontaneously emit a photon and fall back to the ground state.

If many atoms are packed together and separated by a shorter distance than the wavelength of the emitted photon, the light they emit will cancel itself out, and the atoms will stay in their excited state. .

But how can the canceling out of the light a cloud of atoms emits keep those atoms excited state.

It's not really the destructive interference between any emitted photons that traps atoms in excited states, but instead — and here's the wacky part — the possibility that it might happen, which stops the photons from being emitted in the first place?

The destructive interference of the photons that would have been emitted by individual atoms prevents the decay of an excited state collectively shared in the atomic ensemble.".

Many of the excited atoms rapidly decayed through a process called superradiance, which is related to subradiance but instead has atoms combining their emitted light constructively into a super intense flash.

But some atoms lingered in a subradiant, or "dark," state, unable to emit light that would destructively interfere.

As time passed, some atoms in superradiant states also became subradiant, turning the atom cloud increasingly subradiant. .

Once they had found a way of making a subradiant cloud, the researchers jolted the atoms from their dark states by adjusting the optical tweezers, enabling the atoms to emit light without destructive interference.

Only the number of atoms in an excited cloud affected its lifetime — the more atoms there were, the longer it took them to decay back to their ground states. .

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