Atomic Lock: How to Catch Light in a Solar Storm ⚡ экспресс
Detecting photons against the glare of sunlight is a challenge for photon counting. A single rubidium atom, acting as a quantum jump detector (registering changes in the atom's state upon photon absorption), picks out laser photons from a flood of 10¹⁰ solar photons per second. The model of the atom's dynamics was confirmed by experiment. The channel capacity was calculated: 0.5 bits per symbol with 150 photons sent over 10 ms and a background of 1 nW. It's like hearing a whisper at a rock concert. The results are useful for daytime lidars, magnetometry, and optical communication.
A rubidium atom is like a lock that opens only with one key: a particle of light of a strictly defined color. Even under the fiery rain of the sun, where myriads of colorful 'keys' fall, the lock remains silent. But when the right one strikes, the atom gets excited for an instant, and the detector registers a click. This is how researchers managed to count individual photons against a background billions of times brighter.
The secret is extreme color selectivity: the atom lets through only one in a hundred million solar photons — like a whisper amid a roaring crowd. In the experiment, the atom was placed at the intersection of a laser and sunlight. Each rare click carried a bit of data, enabling signals to be transmitted through the day. The power was mere billionths of a watt, yet enough for stable communication.
The roots of the idea lie in the work of Roy Glauber and Serge Haroche on photon counting. Now this opens the door to daytime laser radars, magnetic sensors, and jamming-resistant optics. Meanwhile, the tiny atom doesn't wear out and can serve forever. Surprising fact: every second, 10¹⁸ photons hit a square millimeter, yet the atom picks out only the right ones — as if from all the sand on a beach we were to pluck a single golden grain.
🎯 Every second, about 10¹⁸ particles of sunlight hit each square millimeter of Earth's surface. The atom filter screens out all but a tiny fraction — like a sieve that catches only precious grains.